// SPDX-License-Identifier: GPL-2.0+
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/*
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* Read-Copy Update mechanism for mutual exclusion (tree-based version)
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*
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* Copyright IBM Corporation, 2008
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*
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* Authors: Dipankar Sarma <dipankar@in.ibm.com>
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* Manfred Spraul <manfred@colorfullife.com>
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* Paul E. McKenney <paulmck@linux.ibm.com>
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*
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* Based on the original work by Paul McKenney <paulmck@linux.ibm.com>
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* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
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*
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* For detailed explanation of Read-Copy Update mechanism see -
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* Documentation/RCU
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*/
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#define pr_fmt(fmt) "rcu: " fmt
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/spinlock.h>
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#include <linux/smp.h>
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#include <linux/rcupdate_wait.h>
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#include <linux/interrupt.h>
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#include <linux/sched.h>
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#include <linux/sched/debug.h>
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#include <linux/nmi.h>
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#include <linux/atomic.h>
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#include <linux/bitops.h>
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#include <linux/export.h>
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#include <linux/completion.h>
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#include <linux/moduleparam.h>
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#include <linux/percpu.h>
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#include <linux/notifier.h>
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#include <linux/cpu.h>
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#include <linux/mutex.h>
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#include <linux/time.h>
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#include <linux/kernel_stat.h>
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#include <linux/wait.h>
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#include <linux/kthread.h>
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#include <uapi/linux/sched/types.h>
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#include <linux/prefetch.h>
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#include <linux/delay.h>
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#include <linux/random.h>
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#include <linux/trace_events.h>
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#include <linux/suspend.h>
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#include <linux/ftrace.h>
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#include <linux/tick.h>
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#include <linux/sysrq.h>
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#include <linux/kprobes.h>
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#include <linux/gfp.h>
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#include <linux/oom.h>
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#include <linux/smpboot.h>
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#include <linux/jiffies.h>
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#include <linux/slab.h>
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#include <linux/sched/isolation.h>
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#include <linux/sched/clock.h>
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#include <linux/vmalloc.h>
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#include <linux/mm.h>
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#include <linux/kasan.h>
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#include "../time/tick-internal.h"
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#include "tree.h"
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#include "rcu.h"
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#ifdef MODULE_PARAM_PREFIX
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#undef MODULE_PARAM_PREFIX
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#endif
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#define MODULE_PARAM_PREFIX "rcutree."
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/* Data structures. */
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/*
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* Steal a bit from the bottom of ->dynticks for idle entry/exit
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* control. Initially this is for TLB flushing.
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*/
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#define RCU_DYNTICK_CTRL_MASK 0x1
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#define RCU_DYNTICK_CTRL_CTR (RCU_DYNTICK_CTRL_MASK + 1)
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static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = {
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.dynticks_nesting = 1,
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.dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
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.dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR),
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};
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static struct rcu_state rcu_state = {
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.level = { &rcu_state.node[0] },
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.gp_state = RCU_GP_IDLE,
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.gp_seq = (0UL - 300UL) << RCU_SEQ_CTR_SHIFT,
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.barrier_mutex = __MUTEX_INITIALIZER(rcu_state.barrier_mutex),
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.name = RCU_NAME,
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.abbr = RCU_ABBR,
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.exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex),
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.exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex),
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.ofl_lock = __RAW_SPIN_LOCK_UNLOCKED(rcu_state.ofl_lock),
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};
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/* Dump rcu_node combining tree at boot to verify correct setup. */
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static bool dump_tree;
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module_param(dump_tree, bool, 0444);
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/* By default, use RCU_SOFTIRQ instead of rcuc kthreads. */
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static bool use_softirq = !IS_ENABLED(CONFIG_PREEMPT_RT);
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#ifndef CONFIG_PREEMPT_RT
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module_param(use_softirq, bool, 0444);
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#endif
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/* Control rcu_node-tree auto-balancing at boot time. */
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static bool rcu_fanout_exact;
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module_param(rcu_fanout_exact, bool, 0444);
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/* Increase (but not decrease) the RCU_FANOUT_LEAF at boot time. */
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static int rcu_fanout_leaf = RCU_FANOUT_LEAF;
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module_param(rcu_fanout_leaf, int, 0444);
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int rcu_num_lvls __read_mostly = RCU_NUM_LVLS;
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/* Number of rcu_nodes at specified level. */
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int num_rcu_lvl[] = NUM_RCU_LVL_INIT;
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int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */
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/*
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* The rcu_scheduler_active variable is initialized to the value
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* RCU_SCHEDULER_INACTIVE and transitions RCU_SCHEDULER_INIT just before the
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* first task is spawned. So when this variable is RCU_SCHEDULER_INACTIVE,
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* RCU can assume that there is but one task, allowing RCU to (for example)
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* optimize synchronize_rcu() to a simple barrier(). When this variable
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* is RCU_SCHEDULER_INIT, RCU must actually do all the hard work required
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* to detect real grace periods. This variable is also used to suppress
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* boot-time false positives from lockdep-RCU error checking. Finally, it
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* transitions from RCU_SCHEDULER_INIT to RCU_SCHEDULER_RUNNING after RCU
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* is fully initialized, including all of its kthreads having been spawned.
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*/
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int rcu_scheduler_active __read_mostly;
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EXPORT_SYMBOL_GPL(rcu_scheduler_active);
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/*
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* The rcu_scheduler_fully_active variable transitions from zero to one
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* during the early_initcall() processing, which is after the scheduler
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* is capable of creating new tasks. So RCU processing (for example,
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* creating tasks for RCU priority boosting) must be delayed until after
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* rcu_scheduler_fully_active transitions from zero to one. We also
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* currently delay invocation of any RCU callbacks until after this point.
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*
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* It might later prove better for people registering RCU callbacks during
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* early boot to take responsibility for these callbacks, but one step at
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* a time.
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*/
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static int rcu_scheduler_fully_active __read_mostly;
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static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp,
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unsigned long gps, unsigned long flags);
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static void rcu_init_new_rnp(struct rcu_node *rnp_leaf);
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static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf);
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static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
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static void invoke_rcu_core(void);
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static void rcu_report_exp_rdp(struct rcu_data *rdp);
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static void sync_sched_exp_online_cleanup(int cpu);
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static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp);
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/* rcuc/rcub kthread realtime priority */
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static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0;
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module_param(kthread_prio, int, 0444);
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/* Delay in jiffies for grace-period initialization delays, debug only. */
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static int gp_preinit_delay;
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module_param(gp_preinit_delay, int, 0444);
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static int gp_init_delay;
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module_param(gp_init_delay, int, 0444);
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static int gp_cleanup_delay;
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module_param(gp_cleanup_delay, int, 0444);
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// Add delay to rcu_read_unlock() for strict grace periods.
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static int rcu_unlock_delay;
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#ifdef CONFIG_RCU_STRICT_GRACE_PERIOD
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module_param(rcu_unlock_delay, int, 0444);
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#endif
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/*
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* This rcu parameter is runtime-read-only. It reflects
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* a minimum allowed number of objects which can be cached
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* per-CPU. Object size is equal to one page. This value
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* can be changed at boot time.
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*/
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static int rcu_min_cached_objs = 5;
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module_param(rcu_min_cached_objs, int, 0444);
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/* Retrieve RCU kthreads priority for rcutorture */
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int rcu_get_gp_kthreads_prio(void)
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{
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return kthread_prio;
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}
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EXPORT_SYMBOL_GPL(rcu_get_gp_kthreads_prio);
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/*
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* Number of grace periods between delays, normalized by the duration of
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* the delay. The longer the delay, the more the grace periods between
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* each delay. The reason for this normalization is that it means that,
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* for non-zero delays, the overall slowdown of grace periods is constant
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* regardless of the duration of the delay. This arrangement balances
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* the need for long delays to increase some race probabilities with the
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* need for fast grace periods to increase other race probabilities.
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*/
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#define PER_RCU_NODE_PERIOD 3 /* Number of grace periods between delays. */
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/*
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* Compute the mask of online CPUs for the specified rcu_node structure.
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* This will not be stable unless the rcu_node structure's ->lock is
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* held, but the bit corresponding to the current CPU will be stable
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* in most contexts.
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*/
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static unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp)
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{
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return READ_ONCE(rnp->qsmaskinitnext);
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}
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/*
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* Return true if an RCU grace period is in progress. The READ_ONCE()s
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* permit this function to be invoked without holding the root rcu_node
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* structure's ->lock, but of course results can be subject to change.
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*/
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static int rcu_gp_in_progress(void)
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{
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return rcu_seq_state(rcu_seq_current(&rcu_state.gp_seq));
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}
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/*
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* Return the number of callbacks queued on the specified CPU.
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* Handles both the nocbs and normal cases.
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*/
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static long rcu_get_n_cbs_cpu(int cpu)
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{
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struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
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if (rcu_segcblist_is_enabled(&rdp->cblist))
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return rcu_segcblist_n_cbs(&rdp->cblist);
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return 0;
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}
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void rcu_softirq_qs(void)
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{
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rcu_qs();
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rcu_preempt_deferred_qs(current);
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}
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/*
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* Record entry into an extended quiescent state. This is only to be
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* called when not already in an extended quiescent state, that is,
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* RCU is watching prior to the call to this function and is no longer
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* watching upon return.
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*/
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static noinstr void rcu_dynticks_eqs_enter(void)
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{
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struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
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int seq;
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/*
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* CPUs seeing atomic_add_return() must see prior RCU read-side
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* critical sections, and we also must force ordering with the
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* next idle sojourn.
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*/
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rcu_dynticks_task_trace_enter(); // Before ->dynticks update!
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seq = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
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// RCU is no longer watching. Better be in extended quiescent state!
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WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
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(seq & RCU_DYNTICK_CTRL_CTR));
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/* Better not have special action (TLB flush) pending! */
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WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
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(seq & RCU_DYNTICK_CTRL_MASK));
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}
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/*
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* Record exit from an extended quiescent state. This is only to be
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* called from an extended quiescent state, that is, RCU is not watching
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* prior to the call to this function and is watching upon return.
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*/
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static noinstr void rcu_dynticks_eqs_exit(void)
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{
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struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
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int seq;
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/*
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* CPUs seeing atomic_add_return() must see prior idle sojourns,
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* and we also must force ordering with the next RCU read-side
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* critical section.
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*/
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seq = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
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// RCU is now watching. Better not be in an extended quiescent state!
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rcu_dynticks_task_trace_exit(); // After ->dynticks update!
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WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
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!(seq & RCU_DYNTICK_CTRL_CTR));
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if (seq & RCU_DYNTICK_CTRL_MASK) {
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arch_atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks);
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smp_mb__after_atomic(); /* _exit after clearing mask. */
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}
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}
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/*
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* Reset the current CPU's ->dynticks counter to indicate that the
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* newly onlined CPU is no longer in an extended quiescent state.
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* This will either leave the counter unchanged, or increment it
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* to the next non-quiescent value.
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*
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* The non-atomic test/increment sequence works because the upper bits
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* of the ->dynticks counter are manipulated only by the corresponding CPU,
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* or when the corresponding CPU is offline.
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*/
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static void rcu_dynticks_eqs_online(void)
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{
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struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
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if (atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR)
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return;
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atomic_add(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
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}
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/*
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* Is the current CPU in an extended quiescent state?
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*
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* No ordering, as we are sampling CPU-local information.
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*/
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static __always_inline bool rcu_dynticks_curr_cpu_in_eqs(void)
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{
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struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
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return !(arch_atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR);
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}
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/*
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* Snapshot the ->dynticks counter with full ordering so as to allow
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* stable comparison of this counter with past and future snapshots.
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*/
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static int rcu_dynticks_snap(struct rcu_data *rdp)
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{
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int snap = atomic_add_return(0, &rdp->dynticks);
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return snap & ~RCU_DYNTICK_CTRL_MASK;
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}
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/*
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* Return true if the snapshot returned from rcu_dynticks_snap()
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* indicates that RCU is in an extended quiescent state.
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*/
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static bool rcu_dynticks_in_eqs(int snap)
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{
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return !(snap & RCU_DYNTICK_CTRL_CTR);
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}
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/*
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* Return true if the CPU corresponding to the specified rcu_data
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* structure has spent some time in an extended quiescent state since
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* rcu_dynticks_snap() returned the specified snapshot.
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*/
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static bool rcu_dynticks_in_eqs_since(struct rcu_data *rdp, int snap)
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{
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return snap != rcu_dynticks_snap(rdp);
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}
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/*
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* Return true if the referenced integer is zero while the specified
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* CPU remains within a single extended quiescent state.
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*/
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bool rcu_dynticks_zero_in_eqs(int cpu, int *vp)
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{
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struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
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int snap;
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// If not quiescent, force back to earlier extended quiescent state.
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snap = atomic_read(&rdp->dynticks) & ~(RCU_DYNTICK_CTRL_MASK |
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RCU_DYNTICK_CTRL_CTR);
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smp_rmb(); // Order ->dynticks and *vp reads.
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if (READ_ONCE(*vp))
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return false; // Non-zero, so report failure;
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smp_rmb(); // Order *vp read and ->dynticks re-read.
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// If still in the same extended quiescent state, we are good!
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return snap == (atomic_read(&rdp->dynticks) & ~RCU_DYNTICK_CTRL_MASK);
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}
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/*
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* Set the special (bottom) bit of the specified CPU so that it
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* will take special action (such as flushing its TLB) on the
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* next exit from an extended quiescent state. Returns true if
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* the bit was successfully set, or false if the CPU was not in
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* an extended quiescent state.
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*/
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bool rcu_eqs_special_set(int cpu)
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{
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int old;
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int new;
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int new_old;
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struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
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new_old = atomic_read(&rdp->dynticks);
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do {
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old = new_old;
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if (old & RCU_DYNTICK_CTRL_CTR)
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return false;
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new = old | RCU_DYNTICK_CTRL_MASK;
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new_old = atomic_cmpxchg(&rdp->dynticks, old, new);
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} while (new_old != old);
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return true;
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}
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/*
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* Let the RCU core know that this CPU has gone through the scheduler,
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* which is a quiescent state. This is called when the need for a
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* quiescent state is urgent, so we burn an atomic operation and full
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* memory barriers to let the RCU core know about it, regardless of what
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* this CPU might (or might not) do in the near future.
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*
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* We inform the RCU core by emulating a zero-duration dyntick-idle period.
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*
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* The caller must have disabled interrupts and must not be idle.
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*/
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notrace void rcu_momentary_dyntick_idle(void)
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{
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int special;
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raw_cpu_write(rcu_data.rcu_need_heavy_qs, false);
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special = atomic_add_return(2 * RCU_DYNTICK_CTRL_CTR,
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&this_cpu_ptr(&rcu_data)->dynticks);
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/* It is illegal to call this from idle state. */
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WARN_ON_ONCE(!(special & RCU_DYNTICK_CTRL_CTR));
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rcu_preempt_deferred_qs(current);
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}
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EXPORT_SYMBOL_GPL(rcu_momentary_dyntick_idle);
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/**
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* rcu_is_cpu_rrupt_from_idle - see if 'interrupted' from idle
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*
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* If the current CPU is idle and running at a first-level (not nested)
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* interrupt, or directly, from idle, return true.
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*
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* The caller must have at least disabled IRQs.
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*/
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static int rcu_is_cpu_rrupt_from_idle(void)
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{
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long nesting;
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/*
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* Usually called from the tick; but also used from smp_function_call()
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* for expedited grace periods. This latter can result in running from
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* the idle task, instead of an actual IPI.
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*/
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lockdep_assert_irqs_disabled();
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/* Check for counter underflows */
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RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) < 0,
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"RCU dynticks_nesting counter underflow!");
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RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) <= 0,
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"RCU dynticks_nmi_nesting counter underflow/zero!");
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/* Are we at first interrupt nesting level? */
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nesting = __this_cpu_read(rcu_data.dynticks_nmi_nesting);
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if (nesting > 1)
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return false;
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/*
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* If we're not in an interrupt, we must be in the idle task!
|
*/
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WARN_ON_ONCE(!nesting && !is_idle_task(current));
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/* Does CPU appear to be idle from an RCU standpoint? */
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return __this_cpu_read(rcu_data.dynticks_nesting) == 0;
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}
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#define DEFAULT_RCU_BLIMIT (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 1000 : 10)
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// Maximum callbacks per rcu_do_batch ...
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#define DEFAULT_MAX_RCU_BLIMIT 10000 // ... even during callback flood.
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static long blimit = DEFAULT_RCU_BLIMIT;
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#define DEFAULT_RCU_QHIMARK 10000 // If this many pending, ignore blimit.
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static long qhimark = DEFAULT_RCU_QHIMARK;
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#define DEFAULT_RCU_QLOMARK 100 // Once only this many pending, use blimit.
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static long qlowmark = DEFAULT_RCU_QLOMARK;
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#define DEFAULT_RCU_QOVLD_MULT 2
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#define DEFAULT_RCU_QOVLD (DEFAULT_RCU_QOVLD_MULT * DEFAULT_RCU_QHIMARK)
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static long qovld = DEFAULT_RCU_QOVLD; // If this many pending, hammer QS.
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static long qovld_calc = -1; // No pre-initialization lock acquisitions!
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module_param(blimit, long, 0444);
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module_param(qhimark, long, 0444);
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module_param(qlowmark, long, 0444);
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module_param(qovld, long, 0444);
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static ulong jiffies_till_first_fqs = IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 0 : ULONG_MAX;
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static ulong jiffies_till_next_fqs = ULONG_MAX;
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static bool rcu_kick_kthreads;
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static int rcu_divisor = 7;
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module_param(rcu_divisor, int, 0644);
|
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/* Force an exit from rcu_do_batch() after 3 milliseconds. */
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static long rcu_resched_ns = 3 * NSEC_PER_MSEC;
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module_param(rcu_resched_ns, long, 0644);
|
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/*
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* How long the grace period must be before we start recruiting
|
* quiescent-state help from rcu_note_context_switch().
|
*/
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static ulong jiffies_till_sched_qs = ULONG_MAX;
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module_param(jiffies_till_sched_qs, ulong, 0444);
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static ulong jiffies_to_sched_qs; /* See adjust_jiffies_till_sched_qs(). */
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module_param(jiffies_to_sched_qs, ulong, 0444); /* Display only! */
|
|
/*
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* Make sure that we give the grace-period kthread time to detect any
|
* idle CPUs before taking active measures to force quiescent states.
|
* However, don't go below 100 milliseconds, adjusted upwards for really
|
* large systems.
|
*/
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static void adjust_jiffies_till_sched_qs(void)
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{
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unsigned long j;
|
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/* If jiffies_till_sched_qs was specified, respect the request. */
|
if (jiffies_till_sched_qs != ULONG_MAX) {
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WRITE_ONCE(jiffies_to_sched_qs, jiffies_till_sched_qs);
|
return;
|
}
|
/* Otherwise, set to third fqs scan, but bound below on large system. */
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j = READ_ONCE(jiffies_till_first_fqs) +
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2 * READ_ONCE(jiffies_till_next_fqs);
|
if (j < HZ / 10 + nr_cpu_ids / RCU_JIFFIES_FQS_DIV)
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j = HZ / 10 + nr_cpu_ids / RCU_JIFFIES_FQS_DIV;
|
pr_info("RCU calculated value of scheduler-enlistment delay is %ld jiffies.\n", j);
|
WRITE_ONCE(jiffies_to_sched_qs, j);
|
}
|
|
static int param_set_first_fqs_jiffies(const char *val, const struct kernel_param *kp)
|
{
|
ulong j;
|
int ret = kstrtoul(val, 0, &j);
|
|
if (!ret) {
|
WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : j);
|
adjust_jiffies_till_sched_qs();
|
}
|
return ret;
|
}
|
|
static int param_set_next_fqs_jiffies(const char *val, const struct kernel_param *kp)
|
{
|
ulong j;
|
int ret = kstrtoul(val, 0, &j);
|
|
if (!ret) {
|
WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : (j ?: 1));
|
adjust_jiffies_till_sched_qs();
|
}
|
return ret;
|
}
|
|
static struct kernel_param_ops first_fqs_jiffies_ops = {
|
.set = param_set_first_fqs_jiffies,
|
.get = param_get_ulong,
|
};
|
|
static struct kernel_param_ops next_fqs_jiffies_ops = {
|
.set = param_set_next_fqs_jiffies,
|
.get = param_get_ulong,
|
};
|
|
module_param_cb(jiffies_till_first_fqs, &first_fqs_jiffies_ops, &jiffies_till_first_fqs, 0644);
|
module_param_cb(jiffies_till_next_fqs, &next_fqs_jiffies_ops, &jiffies_till_next_fqs, 0644);
|
module_param(rcu_kick_kthreads, bool, 0644);
|
|
static void force_qs_rnp(int (*f)(struct rcu_data *rdp));
|
static int rcu_pending(int user);
|
|
/*
|
* Return the number of RCU GPs completed thus far for debug & stats.
|
*/
|
unsigned long rcu_get_gp_seq(void)
|
{
|
return READ_ONCE(rcu_state.gp_seq);
|
}
|
EXPORT_SYMBOL_GPL(rcu_get_gp_seq);
|
|
/*
|
* Return the number of RCU expedited batches completed thus far for
|
* debug & stats. Odd numbers mean that a batch is in progress, even
|
* numbers mean idle. The value returned will thus be roughly double
|
* the cumulative batches since boot.
|
*/
|
unsigned long rcu_exp_batches_completed(void)
|
{
|
return rcu_state.expedited_sequence;
|
}
|
EXPORT_SYMBOL_GPL(rcu_exp_batches_completed);
|
|
/*
|
* Return the root node of the rcu_state structure.
|
*/
|
static struct rcu_node *rcu_get_root(void)
|
{
|
return &rcu_state.node[0];
|
}
|
|
/*
|
* Send along grace-period-related data for rcutorture diagnostics.
|
*/
|
void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
|
unsigned long *gp_seq)
|
{
|
switch (test_type) {
|
case RCU_FLAVOR:
|
*flags = READ_ONCE(rcu_state.gp_flags);
|
*gp_seq = rcu_seq_current(&rcu_state.gp_seq);
|
break;
|
default:
|
break;
|
}
|
}
|
EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
|
|
/*
|
* Enter an RCU extended quiescent state, which can be either the
|
* idle loop or adaptive-tickless usermode execution.
|
*
|
* We crowbar the ->dynticks_nmi_nesting field to zero to allow for
|
* the possibility of usermode upcalls having messed up our count
|
* of interrupt nesting level during the prior busy period.
|
*/
|
static noinstr void rcu_eqs_enter(bool user)
|
{
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
|
WARN_ON_ONCE(rdp->dynticks_nmi_nesting != DYNTICK_IRQ_NONIDLE);
|
WRITE_ONCE(rdp->dynticks_nmi_nesting, 0);
|
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
|
rdp->dynticks_nesting == 0);
|
if (rdp->dynticks_nesting != 1) {
|
// RCU will still be watching, so just do accounting and leave.
|
rdp->dynticks_nesting--;
|
return;
|
}
|
|
lockdep_assert_irqs_disabled();
|
instrumentation_begin();
|
trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, atomic_read(&rdp->dynticks));
|
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
|
rdp = this_cpu_ptr(&rcu_data);
|
rcu_prepare_for_idle();
|
rcu_preempt_deferred_qs(current);
|
|
// instrumentation for the noinstr rcu_dynticks_eqs_enter()
|
instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
|
|
instrumentation_end();
|
WRITE_ONCE(rdp->dynticks_nesting, 0); /* Avoid irq-access tearing. */
|
// RCU is watching here ...
|
rcu_dynticks_eqs_enter();
|
// ... but is no longer watching here.
|
rcu_dynticks_task_enter();
|
}
|
|
/**
|
* rcu_idle_enter - inform RCU that current CPU is entering idle
|
*
|
* Enter idle mode, in other words, -leave- the mode in which RCU
|
* read-side critical sections can occur. (Though RCU read-side
|
* critical sections can occur in irq handlers in idle, a possibility
|
* handled by irq_enter() and irq_exit().)
|
*
|
* If you add or remove a call to rcu_idle_enter(), be sure to test with
|
* CONFIG_RCU_EQS_DEBUG=y.
|
*/
|
void rcu_idle_enter(void)
|
{
|
lockdep_assert_irqs_disabled();
|
rcu_eqs_enter(false);
|
}
|
EXPORT_SYMBOL_GPL(rcu_idle_enter);
|
|
#ifdef CONFIG_NO_HZ_FULL
|
/**
|
* rcu_user_enter - inform RCU that we are resuming userspace.
|
*
|
* Enter RCU idle mode right before resuming userspace. No use of RCU
|
* is permitted between this call and rcu_user_exit(). This way the
|
* CPU doesn't need to maintain the tick for RCU maintenance purposes
|
* when the CPU runs in userspace.
|
*
|
* If you add or remove a call to rcu_user_enter(), be sure to test with
|
* CONFIG_RCU_EQS_DEBUG=y.
|
*/
|
noinstr void rcu_user_enter(void)
|
{
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
|
lockdep_assert_irqs_disabled();
|
|
instrumentation_begin();
|
do_nocb_deferred_wakeup(rdp);
|
instrumentation_end();
|
|
rcu_eqs_enter(true);
|
}
|
#endif /* CONFIG_NO_HZ_FULL */
|
|
/**
|
* rcu_nmi_exit - inform RCU of exit from NMI context
|
*
|
* If we are returning from the outermost NMI handler that interrupted an
|
* RCU-idle period, update rdp->dynticks and rdp->dynticks_nmi_nesting
|
* to let the RCU grace-period handling know that the CPU is back to
|
* being RCU-idle.
|
*
|
* If you add or remove a call to rcu_nmi_exit(), be sure to test
|
* with CONFIG_RCU_EQS_DEBUG=y.
|
*/
|
noinstr void rcu_nmi_exit(void)
|
{
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
|
instrumentation_begin();
|
/*
|
* Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
|
* (We are exiting an NMI handler, so RCU better be paying attention
|
* to us!)
|
*/
|
WARN_ON_ONCE(rdp->dynticks_nmi_nesting <= 0);
|
WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs());
|
|
/*
|
* If the nesting level is not 1, the CPU wasn't RCU-idle, so
|
* leave it in non-RCU-idle state.
|
*/
|
if (rdp->dynticks_nmi_nesting != 1) {
|
trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2,
|
atomic_read(&rdp->dynticks));
|
WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */
|
rdp->dynticks_nmi_nesting - 2);
|
instrumentation_end();
|
return;
|
}
|
|
/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
|
trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, atomic_read(&rdp->dynticks));
|
WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
|
|
if (!in_nmi())
|
rcu_prepare_for_idle();
|
|
// instrumentation for the noinstr rcu_dynticks_eqs_enter()
|
instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
|
instrumentation_end();
|
|
// RCU is watching here ...
|
rcu_dynticks_eqs_enter();
|
// ... but is no longer watching here.
|
|
if (!in_nmi())
|
rcu_dynticks_task_enter();
|
}
|
|
/**
|
* rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
|
*
|
* Exit from an interrupt handler, which might possibly result in entering
|
* idle mode, in other words, leaving the mode in which read-side critical
|
* sections can occur. The caller must have disabled interrupts.
|
*
|
* This code assumes that the idle loop never does anything that might
|
* result in unbalanced calls to irq_enter() and irq_exit(). If your
|
* architecture's idle loop violates this assumption, RCU will give you what
|
* you deserve, good and hard. But very infrequently and irreproducibly.
|
*
|
* Use things like work queues to work around this limitation.
|
*
|
* You have been warned.
|
*
|
* If you add or remove a call to rcu_irq_exit(), be sure to test with
|
* CONFIG_RCU_EQS_DEBUG=y.
|
*/
|
void noinstr rcu_irq_exit(void)
|
{
|
lockdep_assert_irqs_disabled();
|
rcu_nmi_exit();
|
}
|
|
/**
|
* rcu_irq_exit_preempt - Inform RCU that current CPU is exiting irq
|
* towards in kernel preemption
|
*
|
* Same as rcu_irq_exit() but has a sanity check that scheduling is safe
|
* from RCU point of view. Invoked from return from interrupt before kernel
|
* preemption.
|
*/
|
void rcu_irq_exit_preempt(void)
|
{
|
lockdep_assert_irqs_disabled();
|
rcu_nmi_exit();
|
|
RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) <= 0,
|
"RCU dynticks_nesting counter underflow/zero!");
|
RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) !=
|
DYNTICK_IRQ_NONIDLE,
|
"Bad RCU dynticks_nmi_nesting counter\n");
|
RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
|
"RCU in extended quiescent state!");
|
}
|
|
#ifdef CONFIG_PROVE_RCU
|
/**
|
* rcu_irq_exit_check_preempt - Validate that scheduling is possible
|
*/
|
void rcu_irq_exit_check_preempt(void)
|
{
|
lockdep_assert_irqs_disabled();
|
|
RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) <= 0,
|
"RCU dynticks_nesting counter underflow/zero!");
|
RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) !=
|
DYNTICK_IRQ_NONIDLE,
|
"Bad RCU dynticks_nmi_nesting counter\n");
|
RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
|
"RCU in extended quiescent state!");
|
}
|
#endif /* #ifdef CONFIG_PROVE_RCU */
|
|
/*
|
* Wrapper for rcu_irq_exit() where interrupts are enabled.
|
*
|
* If you add or remove a call to rcu_irq_exit_irqson(), be sure to test
|
* with CONFIG_RCU_EQS_DEBUG=y.
|
*/
|
void rcu_irq_exit_irqson(void)
|
{
|
unsigned long flags;
|
|
local_irq_save(flags);
|
rcu_irq_exit();
|
local_irq_restore(flags);
|
}
|
|
/*
|
* Exit an RCU extended quiescent state, which can be either the
|
* idle loop or adaptive-tickless usermode execution.
|
*
|
* We crowbar the ->dynticks_nmi_nesting field to DYNTICK_IRQ_NONIDLE to
|
* allow for the possibility of usermode upcalls messing up our count of
|
* interrupt nesting level during the busy period that is just now starting.
|
*/
|
static void noinstr rcu_eqs_exit(bool user)
|
{
|
struct rcu_data *rdp;
|
long oldval;
|
|
lockdep_assert_irqs_disabled();
|
rdp = this_cpu_ptr(&rcu_data);
|
oldval = rdp->dynticks_nesting;
|
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0);
|
if (oldval) {
|
// RCU was already watching, so just do accounting and leave.
|
rdp->dynticks_nesting++;
|
return;
|
}
|
rcu_dynticks_task_exit();
|
// RCU is not watching here ...
|
rcu_dynticks_eqs_exit();
|
// ... but is watching here.
|
instrumentation_begin();
|
|
// instrumentation for the noinstr rcu_dynticks_eqs_exit()
|
instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
|
|
rcu_cleanup_after_idle();
|
trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, atomic_read(&rdp->dynticks));
|
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
|
WRITE_ONCE(rdp->dynticks_nesting, 1);
|
WARN_ON_ONCE(rdp->dynticks_nmi_nesting);
|
WRITE_ONCE(rdp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);
|
instrumentation_end();
|
}
|
|
/**
|
* rcu_idle_exit - inform RCU that current CPU is leaving idle
|
*
|
* Exit idle mode, in other words, -enter- the mode in which RCU
|
* read-side critical sections can occur.
|
*
|
* If you add or remove a call to rcu_idle_exit(), be sure to test with
|
* CONFIG_RCU_EQS_DEBUG=y.
|
*/
|
void rcu_idle_exit(void)
|
{
|
unsigned long flags;
|
|
local_irq_save(flags);
|
rcu_eqs_exit(false);
|
local_irq_restore(flags);
|
}
|
EXPORT_SYMBOL_GPL(rcu_idle_exit);
|
|
#ifdef CONFIG_NO_HZ_FULL
|
/**
|
* rcu_user_exit - inform RCU that we are exiting userspace.
|
*
|
* Exit RCU idle mode while entering the kernel because it can
|
* run a RCU read side critical section anytime.
|
*
|
* If you add or remove a call to rcu_user_exit(), be sure to test with
|
* CONFIG_RCU_EQS_DEBUG=y.
|
*/
|
void noinstr rcu_user_exit(void)
|
{
|
rcu_eqs_exit(1);
|
}
|
|
/**
|
* __rcu_irq_enter_check_tick - Enable scheduler tick on CPU if RCU needs it.
|
*
|
* The scheduler tick is not normally enabled when CPUs enter the kernel
|
* from nohz_full userspace execution. After all, nohz_full userspace
|
* execution is an RCU quiescent state and the time executing in the kernel
|
* is quite short. Except of course when it isn't. And it is not hard to
|
* cause a large system to spend tens of seconds or even minutes looping
|
* in the kernel, which can cause a number of problems, include RCU CPU
|
* stall warnings.
|
*
|
* Therefore, if a nohz_full CPU fails to report a quiescent state
|
* in a timely manner, the RCU grace-period kthread sets that CPU's
|
* ->rcu_urgent_qs flag with the expectation that the next interrupt or
|
* exception will invoke this function, which will turn on the scheduler
|
* tick, which will enable RCU to detect that CPU's quiescent states,
|
* for example, due to cond_resched() calls in CONFIG_PREEMPT=n kernels.
|
* The tick will be disabled once a quiescent state is reported for
|
* this CPU.
|
*
|
* Of course, in carefully tuned systems, there might never be an
|
* interrupt or exception. In that case, the RCU grace-period kthread
|
* will eventually cause one to happen. However, in less carefully
|
* controlled environments, this function allows RCU to get what it
|
* needs without creating otherwise useless interruptions.
|
*/
|
void __rcu_irq_enter_check_tick(void)
|
{
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
|
// If we're here from NMI there's nothing to do.
|
if (in_nmi())
|
return;
|
|
RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
|
"Illegal rcu_irq_enter_check_tick() from extended quiescent state");
|
|
if (!tick_nohz_full_cpu(rdp->cpu) ||
|
!READ_ONCE(rdp->rcu_urgent_qs) ||
|
READ_ONCE(rdp->rcu_forced_tick)) {
|
// RCU doesn't need nohz_full help from this CPU, or it is
|
// already getting that help.
|
return;
|
}
|
|
// We get here only when not in an extended quiescent state and
|
// from interrupts (as opposed to NMIs). Therefore, (1) RCU is
|
// already watching and (2) The fact that we are in an interrupt
|
// handler and that the rcu_node lock is an irq-disabled lock
|
// prevents self-deadlock. So we can safely recheck under the lock.
|
// Note that the nohz_full state currently cannot change.
|
raw_spin_lock_rcu_node(rdp->mynode);
|
if (rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) {
|
// A nohz_full CPU is in the kernel and RCU needs a
|
// quiescent state. Turn on the tick!
|
WRITE_ONCE(rdp->rcu_forced_tick, true);
|
tick_dep_set_cpu(rdp->cpu, TICK_DEP_BIT_RCU);
|
}
|
raw_spin_unlock_rcu_node(rdp->mynode);
|
}
|
#endif /* CONFIG_NO_HZ_FULL */
|
|
/**
|
* rcu_nmi_enter - inform RCU of entry to NMI context
|
*
|
* If the CPU was idle from RCU's viewpoint, update rdp->dynticks and
|
* rdp->dynticks_nmi_nesting to let the RCU grace-period handling know
|
* that the CPU is active. This implementation permits nested NMIs, as
|
* long as the nesting level does not overflow an int. (You will probably
|
* run out of stack space first.)
|
*
|
* If you add or remove a call to rcu_nmi_enter(), be sure to test
|
* with CONFIG_RCU_EQS_DEBUG=y.
|
*/
|
noinstr void rcu_nmi_enter(void)
|
{
|
long incby = 2;
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
|
/* Complain about underflow. */
|
WARN_ON_ONCE(rdp->dynticks_nmi_nesting < 0);
|
|
/*
|
* If idle from RCU viewpoint, atomically increment ->dynticks
|
* to mark non-idle and increment ->dynticks_nmi_nesting by one.
|
* Otherwise, increment ->dynticks_nmi_nesting by two. This means
|
* if ->dynticks_nmi_nesting is equal to one, we are guaranteed
|
* to be in the outermost NMI handler that interrupted an RCU-idle
|
* period (observation due to Andy Lutomirski).
|
*/
|
if (rcu_dynticks_curr_cpu_in_eqs()) {
|
|
if (!in_nmi())
|
rcu_dynticks_task_exit();
|
|
// RCU is not watching here ...
|
rcu_dynticks_eqs_exit();
|
// ... but is watching here.
|
|
if (!in_nmi()) {
|
instrumentation_begin();
|
rcu_cleanup_after_idle();
|
instrumentation_end();
|
}
|
|
instrumentation_begin();
|
// instrumentation for the noinstr rcu_dynticks_curr_cpu_in_eqs()
|
instrument_atomic_read(&rdp->dynticks, sizeof(rdp->dynticks));
|
// instrumentation for the noinstr rcu_dynticks_eqs_exit()
|
instrument_atomic_write(&rdp->dynticks, sizeof(rdp->dynticks));
|
|
incby = 1;
|
} else if (!in_nmi()) {
|
instrumentation_begin();
|
rcu_irq_enter_check_tick();
|
} else {
|
instrumentation_begin();
|
}
|
|
trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
|
rdp->dynticks_nmi_nesting,
|
rdp->dynticks_nmi_nesting + incby, atomic_read(&rdp->dynticks));
|
instrumentation_end();
|
WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */
|
rdp->dynticks_nmi_nesting + incby);
|
barrier();
|
}
|
|
/**
|
* rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
|
*
|
* Enter an interrupt handler, which might possibly result in exiting
|
* idle mode, in other words, entering the mode in which read-side critical
|
* sections can occur. The caller must have disabled interrupts.
|
*
|
* Note that the Linux kernel is fully capable of entering an interrupt
|
* handler that it never exits, for example when doing upcalls to user mode!
|
* This code assumes that the idle loop never does upcalls to user mode.
|
* If your architecture's idle loop does do upcalls to user mode (or does
|
* anything else that results in unbalanced calls to the irq_enter() and
|
* irq_exit() functions), RCU will give you what you deserve, good and hard.
|
* But very infrequently and irreproducibly.
|
*
|
* Use things like work queues to work around this limitation.
|
*
|
* You have been warned.
|
*
|
* If you add or remove a call to rcu_irq_enter(), be sure to test with
|
* CONFIG_RCU_EQS_DEBUG=y.
|
*/
|
noinstr void rcu_irq_enter(void)
|
{
|
lockdep_assert_irqs_disabled();
|
rcu_nmi_enter();
|
}
|
|
/*
|
* Wrapper for rcu_irq_enter() where interrupts are enabled.
|
*
|
* If you add or remove a call to rcu_irq_enter_irqson(), be sure to test
|
* with CONFIG_RCU_EQS_DEBUG=y.
|
*/
|
void rcu_irq_enter_irqson(void)
|
{
|
unsigned long flags;
|
|
local_irq_save(flags);
|
rcu_irq_enter();
|
local_irq_restore(flags);
|
}
|
|
/*
|
* If any sort of urgency was applied to the current CPU (for example,
|
* the scheduler-clock interrupt was enabled on a nohz_full CPU) in order
|
* to get to a quiescent state, disable it.
|
*/
|
static void rcu_disable_urgency_upon_qs(struct rcu_data *rdp)
|
{
|
raw_lockdep_assert_held_rcu_node(rdp->mynode);
|
WRITE_ONCE(rdp->rcu_urgent_qs, false);
|
WRITE_ONCE(rdp->rcu_need_heavy_qs, false);
|
if (tick_nohz_full_cpu(rdp->cpu) && rdp->rcu_forced_tick) {
|
tick_dep_clear_cpu(rdp->cpu, TICK_DEP_BIT_RCU);
|
WRITE_ONCE(rdp->rcu_forced_tick, false);
|
}
|
}
|
|
/**
|
* rcu_is_watching - see if RCU thinks that the current CPU is not idle
|
*
|
* Return true if RCU is watching the running CPU, which means that this
|
* CPU can safely enter RCU read-side critical sections. In other words,
|
* if the current CPU is not in its idle loop or is in an interrupt or
|
* NMI handler, return true.
|
*
|
* Make notrace because it can be called by the internal functions of
|
* ftrace, and making this notrace removes unnecessary recursion calls.
|
*/
|
notrace bool rcu_is_watching(void)
|
{
|
bool ret;
|
|
preempt_disable_notrace();
|
ret = !rcu_dynticks_curr_cpu_in_eqs();
|
preempt_enable_notrace();
|
return ret;
|
}
|
EXPORT_SYMBOL_GPL(rcu_is_watching);
|
|
/*
|
* If a holdout task is actually running, request an urgent quiescent
|
* state from its CPU. This is unsynchronized, so migrations can cause
|
* the request to go to the wrong CPU. Which is OK, all that will happen
|
* is that the CPU's next context switch will be a bit slower and next
|
* time around this task will generate another request.
|
*/
|
void rcu_request_urgent_qs_task(struct task_struct *t)
|
{
|
int cpu;
|
|
barrier();
|
cpu = task_cpu(t);
|
if (!task_curr(t))
|
return; /* This task is not running on that CPU. */
|
smp_store_release(per_cpu_ptr(&rcu_data.rcu_urgent_qs, cpu), true);
|
}
|
|
#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU)
|
|
/*
|
* Is the current CPU online as far as RCU is concerned?
|
*
|
* Disable preemption to avoid false positives that could otherwise
|
* happen due to the current CPU number being sampled, this task being
|
* preempted, its old CPU being taken offline, resuming on some other CPU,
|
* then determining that its old CPU is now offline.
|
*
|
* Disable checking if in an NMI handler because we cannot safely
|
* report errors from NMI handlers anyway. In addition, it is OK to use
|
* RCU on an offline processor during initial boot, hence the check for
|
* rcu_scheduler_fully_active.
|
*/
|
bool rcu_lockdep_current_cpu_online(void)
|
{
|
struct rcu_data *rdp;
|
struct rcu_node *rnp;
|
bool ret = false;
|
|
if (in_nmi() || !rcu_scheduler_fully_active)
|
return true;
|
preempt_disable_notrace();
|
rdp = this_cpu_ptr(&rcu_data);
|
rnp = rdp->mynode;
|
if (rdp->grpmask & rcu_rnp_online_cpus(rnp))
|
ret = true;
|
preempt_enable_notrace();
|
return ret;
|
}
|
EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
|
|
#endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */
|
|
/*
|
* We are reporting a quiescent state on behalf of some other CPU, so
|
* it is our responsibility to check for and handle potential overflow
|
* of the rcu_node ->gp_seq counter with respect to the rcu_data counters.
|
* After all, the CPU might be in deep idle state, and thus executing no
|
* code whatsoever.
|
*/
|
static void rcu_gpnum_ovf(struct rcu_node *rnp, struct rcu_data *rdp)
|
{
|
raw_lockdep_assert_held_rcu_node(rnp);
|
if (ULONG_CMP_LT(rcu_seq_current(&rdp->gp_seq) + ULONG_MAX / 4,
|
rnp->gp_seq))
|
WRITE_ONCE(rdp->gpwrap, true);
|
if (ULONG_CMP_LT(rdp->rcu_iw_gp_seq + ULONG_MAX / 4, rnp->gp_seq))
|
rdp->rcu_iw_gp_seq = rnp->gp_seq + ULONG_MAX / 4;
|
}
|
|
/*
|
* Snapshot the specified CPU's dynticks counter so that we can later
|
* credit them with an implicit quiescent state. Return 1 if this CPU
|
* is in dynticks idle mode, which is an extended quiescent state.
|
*/
|
static int dyntick_save_progress_counter(struct rcu_data *rdp)
|
{
|
rdp->dynticks_snap = rcu_dynticks_snap(rdp);
|
if (rcu_dynticks_in_eqs(rdp->dynticks_snap)) {
|
trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti"));
|
rcu_gpnum_ovf(rdp->mynode, rdp);
|
return 1;
|
}
|
return 0;
|
}
|
|
/*
|
* Return true if the specified CPU has passed through a quiescent
|
* state by virtue of being in or having passed through an dynticks
|
* idle state since the last call to dyntick_save_progress_counter()
|
* for this same CPU, or by virtue of having been offline.
|
*/
|
static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
|
{
|
unsigned long jtsq;
|
bool *rnhqp;
|
bool *ruqp;
|
struct rcu_node *rnp = rdp->mynode;
|
|
/*
|
* If the CPU passed through or entered a dynticks idle phase with
|
* no active irq/NMI handlers, then we can safely pretend that the CPU
|
* already acknowledged the request to pass through a quiescent
|
* state. Either way, that CPU cannot possibly be in an RCU
|
* read-side critical section that started before the beginning
|
* of the current RCU grace period.
|
*/
|
if (rcu_dynticks_in_eqs_since(rdp, rdp->dynticks_snap)) {
|
trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti"));
|
rcu_gpnum_ovf(rnp, rdp);
|
return 1;
|
}
|
|
/*
|
* Complain if a CPU that is considered to be offline from RCU's
|
* perspective has not yet reported a quiescent state. After all,
|
* the offline CPU should have reported a quiescent state during
|
* the CPU-offline process, or, failing that, by rcu_gp_init()
|
* if it ran concurrently with either the CPU going offline or the
|
* last task on a leaf rcu_node structure exiting its RCU read-side
|
* critical section while all CPUs corresponding to that structure
|
* are offline. This added warning detects bugs in any of these
|
* code paths.
|
*
|
* The rcu_node structure's ->lock is held here, which excludes
|
* the relevant portions the CPU-hotplug code, the grace-period
|
* initialization code, and the rcu_read_unlock() code paths.
|
*
|
* For more detail, please refer to the "Hotplug CPU" section
|
* of RCU's Requirements documentation.
|
*/
|
if (WARN_ON_ONCE(!(rdp->grpmask & rcu_rnp_online_cpus(rnp)))) {
|
bool onl;
|
struct rcu_node *rnp1;
|
|
pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n",
|
__func__, rnp->grplo, rnp->grphi, rnp->level,
|
(long)rnp->gp_seq, (long)rnp->completedqs);
|
for (rnp1 = rnp; rnp1; rnp1 = rnp1->parent)
|
pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx ->rcu_gp_init_mask %#lx\n",
|
__func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext, rnp1->rcu_gp_init_mask);
|
onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp));
|
pr_info("%s %d: %c online: %ld(%d) offline: %ld(%d)\n",
|
__func__, rdp->cpu, ".o"[onl],
|
(long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags,
|
(long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags);
|
return 1; /* Break things loose after complaining. */
|
}
|
|
/*
|
* A CPU running for an extended time within the kernel can
|
* delay RCU grace periods: (1) At age jiffies_to_sched_qs,
|
* set .rcu_urgent_qs, (2) At age 2*jiffies_to_sched_qs, set
|
* both .rcu_need_heavy_qs and .rcu_urgent_qs. Note that the
|
* unsynchronized assignments to the per-CPU rcu_need_heavy_qs
|
* variable are safe because the assignments are repeated if this
|
* CPU failed to pass through a quiescent state. This code
|
* also checks .jiffies_resched in case jiffies_to_sched_qs
|
* is set way high.
|
*/
|
jtsq = READ_ONCE(jiffies_to_sched_qs);
|
ruqp = per_cpu_ptr(&rcu_data.rcu_urgent_qs, rdp->cpu);
|
rnhqp = &per_cpu(rcu_data.rcu_need_heavy_qs, rdp->cpu);
|
if (!READ_ONCE(*rnhqp) &&
|
(time_after(jiffies, rcu_state.gp_start + jtsq * 2) ||
|
time_after(jiffies, rcu_state.jiffies_resched) ||
|
rcu_state.cbovld)) {
|
WRITE_ONCE(*rnhqp, true);
|
/* Store rcu_need_heavy_qs before rcu_urgent_qs. */
|
smp_store_release(ruqp, true);
|
} else if (time_after(jiffies, rcu_state.gp_start + jtsq)) {
|
WRITE_ONCE(*ruqp, true);
|
}
|
|
/*
|
* NO_HZ_FULL CPUs can run in-kernel without rcu_sched_clock_irq!
|
* The above code handles this, but only for straight cond_resched().
|
* And some in-kernel loops check need_resched() before calling
|
* cond_resched(), which defeats the above code for CPUs that are
|
* running in-kernel with scheduling-clock interrupts disabled.
|
* So hit them over the head with the resched_cpu() hammer!
|
*/
|
if (tick_nohz_full_cpu(rdp->cpu) &&
|
(time_after(jiffies, READ_ONCE(rdp->last_fqs_resched) + jtsq * 3) ||
|
rcu_state.cbovld)) {
|
WRITE_ONCE(*ruqp, true);
|
resched_cpu(rdp->cpu);
|
WRITE_ONCE(rdp->last_fqs_resched, jiffies);
|
}
|
|
/*
|
* If more than halfway to RCU CPU stall-warning time, invoke
|
* resched_cpu() more frequently to try to loosen things up a bit.
|
* Also check to see if the CPU is getting hammered with interrupts,
|
* but only once per grace period, just to keep the IPIs down to
|
* a dull roar.
|
*/
|
if (time_after(jiffies, rcu_state.jiffies_resched)) {
|
if (time_after(jiffies,
|
READ_ONCE(rdp->last_fqs_resched) + jtsq)) {
|
resched_cpu(rdp->cpu);
|
WRITE_ONCE(rdp->last_fqs_resched, jiffies);
|
}
|
if (IS_ENABLED(CONFIG_IRQ_WORK) &&
|
!rdp->rcu_iw_pending && rdp->rcu_iw_gp_seq != rnp->gp_seq &&
|
(rnp->ffmask & rdp->grpmask)) {
|
init_irq_work(&rdp->rcu_iw, rcu_iw_handler);
|
atomic_set(&rdp->rcu_iw.flags, IRQ_WORK_HARD_IRQ);
|
rdp->rcu_iw_pending = true;
|
rdp->rcu_iw_gp_seq = rnp->gp_seq;
|
irq_work_queue_on(&rdp->rcu_iw, rdp->cpu);
|
}
|
}
|
|
return 0;
|
}
|
|
/* Trace-event wrapper function for trace_rcu_future_grace_period. */
|
static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
|
unsigned long gp_seq_req, const char *s)
|
{
|
trace_rcu_future_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq),
|
gp_seq_req, rnp->level,
|
rnp->grplo, rnp->grphi, s);
|
}
|
|
/*
|
* rcu_start_this_gp - Request the start of a particular grace period
|
* @rnp_start: The leaf node of the CPU from which to start.
|
* @rdp: The rcu_data corresponding to the CPU from which to start.
|
* @gp_seq_req: The gp_seq of the grace period to start.
|
*
|
* Start the specified grace period, as needed to handle newly arrived
|
* callbacks. The required future grace periods are recorded in each
|
* rcu_node structure's ->gp_seq_needed field. Returns true if there
|
* is reason to awaken the grace-period kthread.
|
*
|
* The caller must hold the specified rcu_node structure's ->lock, which
|
* is why the caller is responsible for waking the grace-period kthread.
|
*
|
* Returns true if the GP thread needs to be awakened else false.
|
*/
|
static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp,
|
unsigned long gp_seq_req)
|
{
|
bool ret = false;
|
struct rcu_node *rnp;
|
|
/*
|
* Use funnel locking to either acquire the root rcu_node
|
* structure's lock or bail out if the need for this grace period
|
* has already been recorded -- or if that grace period has in
|
* fact already started. If there is already a grace period in
|
* progress in a non-leaf node, no recording is needed because the
|
* end of the grace period will scan the leaf rcu_node structures.
|
* Note that rnp_start->lock must not be released.
|
*/
|
raw_lockdep_assert_held_rcu_node(rnp_start);
|
trace_rcu_this_gp(rnp_start, rdp, gp_seq_req, TPS("Startleaf"));
|
for (rnp = rnp_start; 1; rnp = rnp->parent) {
|
if (rnp != rnp_start)
|
raw_spin_lock_rcu_node(rnp);
|
if (ULONG_CMP_GE(rnp->gp_seq_needed, gp_seq_req) ||
|
rcu_seq_started(&rnp->gp_seq, gp_seq_req) ||
|
(rnp != rnp_start &&
|
rcu_seq_state(rcu_seq_current(&rnp->gp_seq)))) {
|
trace_rcu_this_gp(rnp, rdp, gp_seq_req,
|
TPS("Prestarted"));
|
goto unlock_out;
|
}
|
WRITE_ONCE(rnp->gp_seq_needed, gp_seq_req);
|
if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq))) {
|
/*
|
* We just marked the leaf or internal node, and a
|
* grace period is in progress, which means that
|
* rcu_gp_cleanup() will see the marking. Bail to
|
* reduce contention.
|
*/
|
trace_rcu_this_gp(rnp_start, rdp, gp_seq_req,
|
TPS("Startedleaf"));
|
goto unlock_out;
|
}
|
if (rnp != rnp_start && rnp->parent != NULL)
|
raw_spin_unlock_rcu_node(rnp);
|
if (!rnp->parent)
|
break; /* At root, and perhaps also leaf. */
|
}
|
|
/* If GP already in progress, just leave, otherwise start one. */
|
if (rcu_gp_in_progress()) {
|
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Startedleafroot"));
|
goto unlock_out;
|
}
|
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Startedroot"));
|
WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags | RCU_GP_FLAG_INIT);
|
WRITE_ONCE(rcu_state.gp_req_activity, jiffies);
|
if (!READ_ONCE(rcu_state.gp_kthread)) {
|
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("NoGPkthread"));
|
goto unlock_out;
|
}
|
trace_rcu_grace_period(rcu_state.name, data_race(rcu_state.gp_seq), TPS("newreq"));
|
ret = true; /* Caller must wake GP kthread. */
|
unlock_out:
|
/* Push furthest requested GP to leaf node and rcu_data structure. */
|
if (ULONG_CMP_LT(gp_seq_req, rnp->gp_seq_needed)) {
|
WRITE_ONCE(rnp_start->gp_seq_needed, rnp->gp_seq_needed);
|
WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed);
|
}
|
if (rnp != rnp_start)
|
raw_spin_unlock_rcu_node(rnp);
|
return ret;
|
}
|
|
/*
|
* Clean up any old requests for the just-ended grace period. Also return
|
* whether any additional grace periods have been requested.
|
*/
|
static bool rcu_future_gp_cleanup(struct rcu_node *rnp)
|
{
|
bool needmore;
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
|
needmore = ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed);
|
if (!needmore)
|
rnp->gp_seq_needed = rnp->gp_seq; /* Avoid counter wrap. */
|
trace_rcu_this_gp(rnp, rdp, rnp->gp_seq,
|
needmore ? TPS("CleanupMore") : TPS("Cleanup"));
|
return needmore;
|
}
|
|
/*
|
* Awaken the grace-period kthread. Don't do a self-awaken (unless in an
|
* interrupt or softirq handler, in which case we just might immediately
|
* sleep upon return, resulting in a grace-period hang), and don't bother
|
* awakening when there is nothing for the grace-period kthread to do
|
* (as in several CPUs raced to awaken, we lost), and finally don't try
|
* to awaken a kthread that has not yet been created. If all those checks
|
* are passed, track some debug information and awaken.
|
*
|
* So why do the self-wakeup when in an interrupt or softirq handler
|
* in the grace-period kthread's context? Because the kthread might have
|
* been interrupted just as it was going to sleep, and just after the final
|
* pre-sleep check of the awaken condition. In this case, a wakeup really
|
* is required, and is therefore supplied.
|
*/
|
static void rcu_gp_kthread_wake(void)
|
{
|
struct task_struct *t = READ_ONCE(rcu_state.gp_kthread);
|
|
if ((current == t && !in_irq() && !in_serving_softirq()) ||
|
!READ_ONCE(rcu_state.gp_flags) || !t)
|
return;
|
WRITE_ONCE(rcu_state.gp_wake_time, jiffies);
|
WRITE_ONCE(rcu_state.gp_wake_seq, READ_ONCE(rcu_state.gp_seq));
|
swake_up_one(&rcu_state.gp_wq);
|
}
|
|
/*
|
* If there is room, assign a ->gp_seq number to any callbacks on this
|
* CPU that have not already been assigned. Also accelerate any callbacks
|
* that were previously assigned a ->gp_seq number that has since proven
|
* to be too conservative, which can happen if callbacks get assigned a
|
* ->gp_seq number while RCU is idle, but with reference to a non-root
|
* rcu_node structure. This function is idempotent, so it does not hurt
|
* to call it repeatedly. Returns an flag saying that we should awaken
|
* the RCU grace-period kthread.
|
*
|
* The caller must hold rnp->lock with interrupts disabled.
|
*/
|
static bool rcu_accelerate_cbs(struct rcu_node *rnp, struct rcu_data *rdp)
|
{
|
unsigned long gp_seq_req;
|
bool ret = false;
|
|
rcu_lockdep_assert_cblist_protected(rdp);
|
raw_lockdep_assert_held_rcu_node(rnp);
|
|
/* If no pending (not yet ready to invoke) callbacks, nothing to do. */
|
if (!rcu_segcblist_pend_cbs(&rdp->cblist))
|
return false;
|
|
/*
|
* Callbacks are often registered with incomplete grace-period
|
* information. Something about the fact that getting exact
|
* information requires acquiring a global lock... RCU therefore
|
* makes a conservative estimate of the grace period number at which
|
* a given callback will become ready to invoke. The following
|
* code checks this estimate and improves it when possible, thus
|
* accelerating callback invocation to an earlier grace-period
|
* number.
|
*/
|
gp_seq_req = rcu_seq_snap(&rcu_state.gp_seq);
|
if (rcu_segcblist_accelerate(&rdp->cblist, gp_seq_req))
|
ret = rcu_start_this_gp(rnp, rdp, gp_seq_req);
|
|
/* Trace depending on how much we were able to accelerate. */
|
if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL))
|
trace_rcu_grace_period(rcu_state.name, gp_seq_req, TPS("AccWaitCB"));
|
else
|
trace_rcu_grace_period(rcu_state.name, gp_seq_req, TPS("AccReadyCB"));
|
|
return ret;
|
}
|
|
/*
|
* Similar to rcu_accelerate_cbs(), but does not require that the leaf
|
* rcu_node structure's ->lock be held. It consults the cached value
|
* of ->gp_seq_needed in the rcu_data structure, and if that indicates
|
* that a new grace-period request be made, invokes rcu_accelerate_cbs()
|
* while holding the leaf rcu_node structure's ->lock.
|
*/
|
static void rcu_accelerate_cbs_unlocked(struct rcu_node *rnp,
|
struct rcu_data *rdp)
|
{
|
unsigned long c;
|
bool needwake;
|
|
rcu_lockdep_assert_cblist_protected(rdp);
|
c = rcu_seq_snap(&rcu_state.gp_seq);
|
if (!READ_ONCE(rdp->gpwrap) && ULONG_CMP_GE(rdp->gp_seq_needed, c)) {
|
/* Old request still live, so mark recent callbacks. */
|
(void)rcu_segcblist_accelerate(&rdp->cblist, c);
|
return;
|
}
|
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
|
needwake = rcu_accelerate_cbs(rnp, rdp);
|
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
|
if (needwake)
|
rcu_gp_kthread_wake();
|
}
|
|
/*
|
* Move any callbacks whose grace period has completed to the
|
* RCU_DONE_TAIL sublist, then compact the remaining sublists and
|
* assign ->gp_seq numbers to any callbacks in the RCU_NEXT_TAIL
|
* sublist. This function is idempotent, so it does not hurt to
|
* invoke it repeatedly. As long as it is not invoked -too- often...
|
* Returns true if the RCU grace-period kthread needs to be awakened.
|
*
|
* The caller must hold rnp->lock with interrupts disabled.
|
*/
|
static bool rcu_advance_cbs(struct rcu_node *rnp, struct rcu_data *rdp)
|
{
|
rcu_lockdep_assert_cblist_protected(rdp);
|
raw_lockdep_assert_held_rcu_node(rnp);
|
|
/* If no pending (not yet ready to invoke) callbacks, nothing to do. */
|
if (!rcu_segcblist_pend_cbs(&rdp->cblist))
|
return false;
|
|
/*
|
* Find all callbacks whose ->gp_seq numbers indicate that they
|
* are ready to invoke, and put them into the RCU_DONE_TAIL sublist.
|
*/
|
rcu_segcblist_advance(&rdp->cblist, rnp->gp_seq);
|
|
/* Classify any remaining callbacks. */
|
return rcu_accelerate_cbs(rnp, rdp);
|
}
|
|
/*
|
* Move and classify callbacks, but only if doing so won't require
|
* that the RCU grace-period kthread be awakened.
|
*/
|
static void __maybe_unused rcu_advance_cbs_nowake(struct rcu_node *rnp,
|
struct rcu_data *rdp)
|
{
|
rcu_lockdep_assert_cblist_protected(rdp);
|
if (!rcu_seq_state(rcu_seq_current(&rnp->gp_seq)) || !raw_spin_trylock_rcu_node(rnp))
|
return;
|
// The grace period cannot end while we hold the rcu_node lock.
|
if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq)))
|
WARN_ON_ONCE(rcu_advance_cbs(rnp, rdp));
|
raw_spin_unlock_rcu_node(rnp);
|
}
|
|
/*
|
* In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels, attempt to generate a
|
* quiescent state. This is intended to be invoked when the CPU notices
|
* a new grace period.
|
*/
|
static void rcu_strict_gp_check_qs(void)
|
{
|
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) {
|
rcu_read_lock();
|
rcu_read_unlock();
|
}
|
}
|
|
/*
|
* Update CPU-local rcu_data state to record the beginnings and ends of
|
* grace periods. The caller must hold the ->lock of the leaf rcu_node
|
* structure corresponding to the current CPU, and must have irqs disabled.
|
* Returns true if the grace-period kthread needs to be awakened.
|
*/
|
static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp)
|
{
|
bool ret = false;
|
bool need_qs;
|
const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
|
rcu_segcblist_is_offloaded(&rdp->cblist);
|
|
raw_lockdep_assert_held_rcu_node(rnp);
|
|
if (rdp->gp_seq == rnp->gp_seq)
|
return false; /* Nothing to do. */
|
|
/* Handle the ends of any preceding grace periods first. */
|
if (rcu_seq_completed_gp(rdp->gp_seq, rnp->gp_seq) ||
|
unlikely(READ_ONCE(rdp->gpwrap))) {
|
if (!offloaded)
|
ret = rcu_advance_cbs(rnp, rdp); /* Advance CBs. */
|
rdp->core_needs_qs = false;
|
trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuend"));
|
} else {
|
if (!offloaded)
|
ret = rcu_accelerate_cbs(rnp, rdp); /* Recent CBs. */
|
if (rdp->core_needs_qs)
|
rdp->core_needs_qs = !!(rnp->qsmask & rdp->grpmask);
|
}
|
|
/* Now handle the beginnings of any new-to-this-CPU grace periods. */
|
if (rcu_seq_new_gp(rdp->gp_seq, rnp->gp_seq) ||
|
unlikely(READ_ONCE(rdp->gpwrap))) {
|
/*
|
* If the current grace period is waiting for this CPU,
|
* set up to detect a quiescent state, otherwise don't
|
* go looking for one.
|
*/
|
trace_rcu_grace_period(rcu_state.name, rnp->gp_seq, TPS("cpustart"));
|
need_qs = !!(rnp->qsmask & rdp->grpmask);
|
rdp->cpu_no_qs.b.norm = need_qs;
|
rdp->core_needs_qs = need_qs;
|
zero_cpu_stall_ticks(rdp);
|
}
|
rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */
|
if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || rdp->gpwrap)
|
WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed);
|
WRITE_ONCE(rdp->gpwrap, false);
|
rcu_gpnum_ovf(rnp, rdp);
|
return ret;
|
}
|
|
static void note_gp_changes(struct rcu_data *rdp)
|
{
|
unsigned long flags;
|
bool needwake;
|
struct rcu_node *rnp;
|
|
local_irq_save(flags);
|
rnp = rdp->mynode;
|
if ((rdp->gp_seq == rcu_seq_current(&rnp->gp_seq) &&
|
!unlikely(READ_ONCE(rdp->gpwrap))) || /* w/out lock. */
|
!raw_spin_trylock_rcu_node(rnp)) { /* irqs already off, so later. */
|
local_irq_restore(flags);
|
return;
|
}
|
needwake = __note_gp_changes(rnp, rdp);
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
rcu_strict_gp_check_qs();
|
if (needwake)
|
rcu_gp_kthread_wake();
|
}
|
|
static void rcu_gp_slow(int delay)
|
{
|
if (delay > 0 &&
|
!(rcu_seq_ctr(rcu_state.gp_seq) %
|
(rcu_num_nodes * PER_RCU_NODE_PERIOD * delay)))
|
schedule_timeout_idle(delay);
|
}
|
|
static unsigned long sleep_duration;
|
|
/* Allow rcutorture to stall the grace-period kthread. */
|
void rcu_gp_set_torture_wait(int duration)
|
{
|
if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST) && duration > 0)
|
WRITE_ONCE(sleep_duration, duration);
|
}
|
EXPORT_SYMBOL_GPL(rcu_gp_set_torture_wait);
|
|
/* Actually implement the aforementioned wait. */
|
static void rcu_gp_torture_wait(void)
|
{
|
unsigned long duration;
|
|
if (!IS_ENABLED(CONFIG_RCU_TORTURE_TEST))
|
return;
|
duration = xchg(&sleep_duration, 0UL);
|
if (duration > 0) {
|
pr_alert("%s: Waiting %lu jiffies\n", __func__, duration);
|
schedule_timeout_idle(duration);
|
pr_alert("%s: Wait complete\n", __func__);
|
}
|
}
|
|
/*
|
* Handler for on_each_cpu() to invoke the target CPU's RCU core
|
* processing.
|
*/
|
static void rcu_strict_gp_boundary(void *unused)
|
{
|
invoke_rcu_core();
|
}
|
|
/*
|
* Initialize a new grace period. Return false if no grace period required.
|
*/
|
static bool rcu_gp_init(void)
|
{
|
unsigned long flags;
|
unsigned long oldmask;
|
unsigned long mask;
|
struct rcu_data *rdp;
|
struct rcu_node *rnp = rcu_get_root();
|
|
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
raw_spin_lock_irq_rcu_node(rnp);
|
if (!READ_ONCE(rcu_state.gp_flags)) {
|
/* Spurious wakeup, tell caller to go back to sleep. */
|
raw_spin_unlock_irq_rcu_node(rnp);
|
return false;
|
}
|
WRITE_ONCE(rcu_state.gp_flags, 0); /* Clear all flags: New GP. */
|
|
if (WARN_ON_ONCE(rcu_gp_in_progress())) {
|
/*
|
* Grace period already in progress, don't start another.
|
* Not supposed to be able to happen.
|
*/
|
raw_spin_unlock_irq_rcu_node(rnp);
|
return false;
|
}
|
|
/* Advance to a new grace period and initialize state. */
|
record_gp_stall_check_time();
|
/* Record GP times before starting GP, hence rcu_seq_start(). */
|
rcu_seq_start(&rcu_state.gp_seq);
|
ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq);
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("start"));
|
raw_spin_unlock_irq_rcu_node(rnp);
|
|
/*
|
* Apply per-leaf buffered online and offline operations to
|
* the rcu_node tree. Note that this new grace period need not
|
* wait for subsequent online CPUs, and that RCU hooks in the CPU
|
* offlining path, when combined with checks in this function,
|
* will handle CPUs that are currently going offline or that will
|
* go offline later. Please also refer to "Hotplug CPU" section
|
* of RCU's Requirements documentation.
|
*/
|
rcu_state.gp_state = RCU_GP_ONOFF;
|
rcu_for_each_leaf_node(rnp) {
|
raw_spin_lock(&rcu_state.ofl_lock);
|
raw_spin_lock_irq_rcu_node(rnp);
|
if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
|
!rnp->wait_blkd_tasks) {
|
/* Nothing to do on this leaf rcu_node structure. */
|
raw_spin_unlock_irq_rcu_node(rnp);
|
raw_spin_unlock(&rcu_state.ofl_lock);
|
continue;
|
}
|
|
/* Record old state, apply changes to ->qsmaskinit field. */
|
oldmask = rnp->qsmaskinit;
|
rnp->qsmaskinit = rnp->qsmaskinitnext;
|
|
/* If zero-ness of ->qsmaskinit changed, propagate up tree. */
|
if (!oldmask != !rnp->qsmaskinit) {
|
if (!oldmask) { /* First online CPU for rcu_node. */
|
if (!rnp->wait_blkd_tasks) /* Ever offline? */
|
rcu_init_new_rnp(rnp);
|
} else if (rcu_preempt_has_tasks(rnp)) {
|
rnp->wait_blkd_tasks = true; /* blocked tasks */
|
} else { /* Last offline CPU and can propagate. */
|
rcu_cleanup_dead_rnp(rnp);
|
}
|
}
|
|
/*
|
* If all waited-on tasks from prior grace period are
|
* done, and if all this rcu_node structure's CPUs are
|
* still offline, propagate up the rcu_node tree and
|
* clear ->wait_blkd_tasks. Otherwise, if one of this
|
* rcu_node structure's CPUs has since come back online,
|
* simply clear ->wait_blkd_tasks.
|
*/
|
if (rnp->wait_blkd_tasks &&
|
(!rcu_preempt_has_tasks(rnp) || rnp->qsmaskinit)) {
|
rnp->wait_blkd_tasks = false;
|
if (!rnp->qsmaskinit)
|
rcu_cleanup_dead_rnp(rnp);
|
}
|
|
raw_spin_unlock_irq_rcu_node(rnp);
|
raw_spin_unlock(&rcu_state.ofl_lock);
|
}
|
rcu_gp_slow(gp_preinit_delay); /* Races with CPU hotplug. */
|
|
/*
|
* Set the quiescent-state-needed bits in all the rcu_node
|
* structures for all currently online CPUs in breadth-first
|
* order, starting from the root rcu_node structure, relying on the
|
* layout of the tree within the rcu_state.node[] array. Note that
|
* other CPUs will access only the leaves of the hierarchy, thus
|
* seeing that no grace period is in progress, at least until the
|
* corresponding leaf node has been initialized.
|
*
|
* The grace period cannot complete until the initialization
|
* process finishes, because this kthread handles both.
|
*/
|
rcu_state.gp_state = RCU_GP_INIT;
|
rcu_for_each_node_breadth_first(rnp) {
|
rcu_gp_slow(gp_init_delay);
|
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
rdp = this_cpu_ptr(&rcu_data);
|
rcu_preempt_check_blocked_tasks(rnp);
|
rnp->qsmask = rnp->qsmaskinit;
|
WRITE_ONCE(rnp->gp_seq, rcu_state.gp_seq);
|
if (rnp == rdp->mynode)
|
(void)__note_gp_changes(rnp, rdp);
|
rcu_preempt_boost_start_gp(rnp);
|
trace_rcu_grace_period_init(rcu_state.name, rnp->gp_seq,
|
rnp->level, rnp->grplo,
|
rnp->grphi, rnp->qsmask);
|
/* Quiescent states for tasks on any now-offline CPUs. */
|
mask = rnp->qsmask & ~rnp->qsmaskinitnext;
|
rnp->rcu_gp_init_mask = mask;
|
if ((mask || rnp->wait_blkd_tasks) && rcu_is_leaf_node(rnp))
|
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
|
else
|
raw_spin_unlock_irq_rcu_node(rnp);
|
cond_resched_tasks_rcu_qs();
|
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
}
|
|
// If strict, make all CPUs aware of new grace period.
|
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
|
on_each_cpu(rcu_strict_gp_boundary, NULL, 0);
|
|
return true;
|
}
|
|
/*
|
* Helper function for swait_event_idle_exclusive() wakeup at force-quiescent-state
|
* time.
|
*/
|
static bool rcu_gp_fqs_check_wake(int *gfp)
|
{
|
struct rcu_node *rnp = rcu_get_root();
|
|
// If under overload conditions, force an immediate FQS scan.
|
if (*gfp & RCU_GP_FLAG_OVLD)
|
return true;
|
|
// Someone like call_rcu() requested a force-quiescent-state scan.
|
*gfp = READ_ONCE(rcu_state.gp_flags);
|
if (*gfp & RCU_GP_FLAG_FQS)
|
return true;
|
|
// The current grace period has completed.
|
if (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp))
|
return true;
|
|
return false;
|
}
|
|
/*
|
* Do one round of quiescent-state forcing.
|
*/
|
static void rcu_gp_fqs(bool first_time)
|
{
|
struct rcu_node *rnp = rcu_get_root();
|
|
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
WRITE_ONCE(rcu_state.n_force_qs, rcu_state.n_force_qs + 1);
|
if (first_time) {
|
/* Collect dyntick-idle snapshots. */
|
force_qs_rnp(dyntick_save_progress_counter);
|
} else {
|
/* Handle dyntick-idle and offline CPUs. */
|
force_qs_rnp(rcu_implicit_dynticks_qs);
|
}
|
/* Clear flag to prevent immediate re-entry. */
|
if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) {
|
raw_spin_lock_irq_rcu_node(rnp);
|
WRITE_ONCE(rcu_state.gp_flags,
|
READ_ONCE(rcu_state.gp_flags) & ~RCU_GP_FLAG_FQS);
|
raw_spin_unlock_irq_rcu_node(rnp);
|
}
|
}
|
|
/*
|
* Loop doing repeated quiescent-state forcing until the grace period ends.
|
*/
|
static void rcu_gp_fqs_loop(void)
|
{
|
bool first_gp_fqs;
|
int gf = 0;
|
unsigned long j;
|
int ret;
|
struct rcu_node *rnp = rcu_get_root();
|
|
first_gp_fqs = true;
|
j = READ_ONCE(jiffies_till_first_fqs);
|
if (rcu_state.cbovld)
|
gf = RCU_GP_FLAG_OVLD;
|
ret = 0;
|
for (;;) {
|
if (!ret) {
|
rcu_state.jiffies_force_qs = jiffies + j;
|
WRITE_ONCE(rcu_state.jiffies_kick_kthreads,
|
jiffies + (j ? 3 * j : 2));
|
}
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
|
TPS("fqswait"));
|
rcu_state.gp_state = RCU_GP_WAIT_FQS;
|
ret = swait_event_idle_timeout_exclusive(
|
rcu_state.gp_wq, rcu_gp_fqs_check_wake(&gf), j);
|
rcu_gp_torture_wait();
|
rcu_state.gp_state = RCU_GP_DOING_FQS;
|
/* Locking provides needed memory barriers. */
|
/* If grace period done, leave loop. */
|
if (!READ_ONCE(rnp->qsmask) &&
|
!rcu_preempt_blocked_readers_cgp(rnp))
|
break;
|
/* If time for quiescent-state forcing, do it. */
|
if (!time_after(rcu_state.jiffies_force_qs, jiffies) ||
|
(gf & (RCU_GP_FLAG_FQS | RCU_GP_FLAG_OVLD))) {
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
|
TPS("fqsstart"));
|
rcu_gp_fqs(first_gp_fqs);
|
gf = 0;
|
if (first_gp_fqs) {
|
first_gp_fqs = false;
|
gf = rcu_state.cbovld ? RCU_GP_FLAG_OVLD : 0;
|
}
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
|
TPS("fqsend"));
|
cond_resched_tasks_rcu_qs();
|
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
ret = 0; /* Force full wait till next FQS. */
|
j = READ_ONCE(jiffies_till_next_fqs);
|
} else {
|
/* Deal with stray signal. */
|
cond_resched_tasks_rcu_qs();
|
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
WARN_ON(signal_pending(current));
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
|
TPS("fqswaitsig"));
|
ret = 1; /* Keep old FQS timing. */
|
j = jiffies;
|
if (time_after(jiffies, rcu_state.jiffies_force_qs))
|
j = 1;
|
else
|
j = rcu_state.jiffies_force_qs - j;
|
gf = 0;
|
}
|
}
|
}
|
|
/*
|
* Clean up after the old grace period.
|
*/
|
static void rcu_gp_cleanup(void)
|
{
|
int cpu;
|
bool needgp = false;
|
unsigned long gp_duration;
|
unsigned long new_gp_seq;
|
bool offloaded;
|
struct rcu_data *rdp;
|
struct rcu_node *rnp = rcu_get_root();
|
struct swait_queue_head *sq;
|
|
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
raw_spin_lock_irq_rcu_node(rnp);
|
rcu_state.gp_end = jiffies;
|
gp_duration = rcu_state.gp_end - rcu_state.gp_start;
|
if (gp_duration > rcu_state.gp_max)
|
rcu_state.gp_max = gp_duration;
|
|
/*
|
* We know the grace period is complete, but to everyone else
|
* it appears to still be ongoing. But it is also the case
|
* that to everyone else it looks like there is nothing that
|
* they can do to advance the grace period. It is therefore
|
* safe for us to drop the lock in order to mark the grace
|
* period as completed in all of the rcu_node structures.
|
*/
|
raw_spin_unlock_irq_rcu_node(rnp);
|
|
/*
|
* Propagate new ->gp_seq value to rcu_node structures so that
|
* other CPUs don't have to wait until the start of the next grace
|
* period to process their callbacks. This also avoids some nasty
|
* RCU grace-period initialization races by forcing the end of
|
* the current grace period to be completely recorded in all of
|
* the rcu_node structures before the beginning of the next grace
|
* period is recorded in any of the rcu_node structures.
|
*/
|
new_gp_seq = rcu_state.gp_seq;
|
rcu_seq_end(&new_gp_seq);
|
rcu_for_each_node_breadth_first(rnp) {
|
raw_spin_lock_irq_rcu_node(rnp);
|
if (WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)))
|
dump_blkd_tasks(rnp, 10);
|
WARN_ON_ONCE(rnp->qsmask);
|
WRITE_ONCE(rnp->gp_seq, new_gp_seq);
|
rdp = this_cpu_ptr(&rcu_data);
|
if (rnp == rdp->mynode)
|
needgp = __note_gp_changes(rnp, rdp) || needgp;
|
/* smp_mb() provided by prior unlock-lock pair. */
|
needgp = rcu_future_gp_cleanup(rnp) || needgp;
|
// Reset overload indication for CPUs no longer overloaded
|
if (rcu_is_leaf_node(rnp))
|
for_each_leaf_node_cpu_mask(rnp, cpu, rnp->cbovldmask) {
|
rdp = per_cpu_ptr(&rcu_data, cpu);
|
check_cb_ovld_locked(rdp, rnp);
|
}
|
sq = rcu_nocb_gp_get(rnp);
|
raw_spin_unlock_irq_rcu_node(rnp);
|
rcu_nocb_gp_cleanup(sq);
|
cond_resched_tasks_rcu_qs();
|
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
rcu_gp_slow(gp_cleanup_delay);
|
}
|
rnp = rcu_get_root();
|
raw_spin_lock_irq_rcu_node(rnp); /* GP before ->gp_seq update. */
|
|
/* Declare grace period done, trace first to use old GP number. */
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("end"));
|
rcu_seq_end(&rcu_state.gp_seq);
|
ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq);
|
rcu_state.gp_state = RCU_GP_IDLE;
|
/* Check for GP requests since above loop. */
|
rdp = this_cpu_ptr(&rcu_data);
|
if (!needgp && ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed)) {
|
trace_rcu_this_gp(rnp, rdp, rnp->gp_seq_needed,
|
TPS("CleanupMore"));
|
needgp = true;
|
}
|
/* Advance CBs to reduce false positives below. */
|
offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
|
rcu_segcblist_is_offloaded(&rdp->cblist);
|
if ((offloaded || !rcu_accelerate_cbs(rnp, rdp)) && needgp) {
|
WRITE_ONCE(rcu_state.gp_flags, RCU_GP_FLAG_INIT);
|
WRITE_ONCE(rcu_state.gp_req_activity, jiffies);
|
trace_rcu_grace_period(rcu_state.name,
|
rcu_state.gp_seq,
|
TPS("newreq"));
|
} else {
|
WRITE_ONCE(rcu_state.gp_flags,
|
rcu_state.gp_flags & RCU_GP_FLAG_INIT);
|
}
|
raw_spin_unlock_irq_rcu_node(rnp);
|
|
// If strict, make all CPUs aware of the end of the old grace period.
|
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
|
on_each_cpu(rcu_strict_gp_boundary, NULL, 0);
|
}
|
|
/*
|
* Body of kthread that handles grace periods.
|
*/
|
static int __noreturn rcu_gp_kthread(void *unused)
|
{
|
rcu_bind_gp_kthread();
|
for (;;) {
|
|
/* Handle grace-period start. */
|
for (;;) {
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
|
TPS("reqwait"));
|
rcu_state.gp_state = RCU_GP_WAIT_GPS;
|
swait_event_idle_exclusive(rcu_state.gp_wq,
|
READ_ONCE(rcu_state.gp_flags) &
|
RCU_GP_FLAG_INIT);
|
rcu_gp_torture_wait();
|
rcu_state.gp_state = RCU_GP_DONE_GPS;
|
/* Locking provides needed memory barrier. */
|
if (rcu_gp_init())
|
break;
|
cond_resched_tasks_rcu_qs();
|
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
WARN_ON(signal_pending(current));
|
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
|
TPS("reqwaitsig"));
|
}
|
|
/* Handle quiescent-state forcing. */
|
rcu_gp_fqs_loop();
|
|
/* Handle grace-period end. */
|
rcu_state.gp_state = RCU_GP_CLEANUP;
|
rcu_gp_cleanup();
|
rcu_state.gp_state = RCU_GP_CLEANED;
|
}
|
}
|
|
/*
|
* Report a full set of quiescent states to the rcu_state data structure.
|
* Invoke rcu_gp_kthread_wake() to awaken the grace-period kthread if
|
* another grace period is required. Whether we wake the grace-period
|
* kthread or it awakens itself for the next round of quiescent-state
|
* forcing, that kthread will clean up after the just-completed grace
|
* period. Note that the caller must hold rnp->lock, which is released
|
* before return.
|
*/
|
static void rcu_report_qs_rsp(unsigned long flags)
|
__releases(rcu_get_root()->lock)
|
{
|
raw_lockdep_assert_held_rcu_node(rcu_get_root());
|
WARN_ON_ONCE(!rcu_gp_in_progress());
|
WRITE_ONCE(rcu_state.gp_flags,
|
READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS);
|
raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(), flags);
|
rcu_gp_kthread_wake();
|
}
|
|
/*
|
* Similar to rcu_report_qs_rdp(), for which it is a helper function.
|
* Allows quiescent states for a group of CPUs to be reported at one go
|
* to the specified rcu_node structure, though all the CPUs in the group
|
* must be represented by the same rcu_node structure (which need not be a
|
* leaf rcu_node structure, though it often will be). The gps parameter
|
* is the grace-period snapshot, which means that the quiescent states
|
* are valid only if rnp->gp_seq is equal to gps. That structure's lock
|
* must be held upon entry, and it is released before return.
|
*
|
* As a special case, if mask is zero, the bit-already-cleared check is
|
* disabled. This allows propagating quiescent state due to resumed tasks
|
* during grace-period initialization.
|
*/
|
static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp,
|
unsigned long gps, unsigned long flags)
|
__releases(rnp->lock)
|
{
|
unsigned long oldmask = 0;
|
struct rcu_node *rnp_c;
|
|
raw_lockdep_assert_held_rcu_node(rnp);
|
|
/* Walk up the rcu_node hierarchy. */
|
for (;;) {
|
if ((!(rnp->qsmask & mask) && mask) || rnp->gp_seq != gps) {
|
|
/*
|
* Our bit has already been cleared, or the
|
* relevant grace period is already over, so done.
|
*/
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
return;
|
}
|
WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */
|
WARN_ON_ONCE(!rcu_is_leaf_node(rnp) &&
|
rcu_preempt_blocked_readers_cgp(rnp));
|
WRITE_ONCE(rnp->qsmask, rnp->qsmask & ~mask);
|
trace_rcu_quiescent_state_report(rcu_state.name, rnp->gp_seq,
|
mask, rnp->qsmask, rnp->level,
|
rnp->grplo, rnp->grphi,
|
!!rnp->gp_tasks);
|
if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
|
|
/* Other bits still set at this level, so done. */
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
return;
|
}
|
rnp->completedqs = rnp->gp_seq;
|
mask = rnp->grpmask;
|
if (rnp->parent == NULL) {
|
|
/* No more levels. Exit loop holding root lock. */
|
|
break;
|
}
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
rnp_c = rnp;
|
rnp = rnp->parent;
|
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
oldmask = READ_ONCE(rnp_c->qsmask);
|
}
|
|
/*
|
* Get here if we are the last CPU to pass through a quiescent
|
* state for this grace period. Invoke rcu_report_qs_rsp()
|
* to clean up and start the next grace period if one is needed.
|
*/
|
rcu_report_qs_rsp(flags); /* releases rnp->lock. */
|
}
|
|
/*
|
* Record a quiescent state for all tasks that were previously queued
|
* on the specified rcu_node structure and that were blocking the current
|
* RCU grace period. The caller must hold the corresponding rnp->lock with
|
* irqs disabled, and this lock is released upon return, but irqs remain
|
* disabled.
|
*/
|
static void __maybe_unused
|
rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
|
__releases(rnp->lock)
|
{
|
unsigned long gps;
|
unsigned long mask;
|
struct rcu_node *rnp_p;
|
|
raw_lockdep_assert_held_rcu_node(rnp);
|
if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT_RCU)) ||
|
WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)) ||
|
rnp->qsmask != 0) {
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
return; /* Still need more quiescent states! */
|
}
|
|
rnp->completedqs = rnp->gp_seq;
|
rnp_p = rnp->parent;
|
if (rnp_p == NULL) {
|
/*
|
* Only one rcu_node structure in the tree, so don't
|
* try to report up to its nonexistent parent!
|
*/
|
rcu_report_qs_rsp(flags);
|
return;
|
}
|
|
/* Report up the rest of the hierarchy, tracking current ->gp_seq. */
|
gps = rnp->gp_seq;
|
mask = rnp->grpmask;
|
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
|
raw_spin_lock_rcu_node(rnp_p); /* irqs already disabled. */
|
rcu_report_qs_rnp(mask, rnp_p, gps, flags);
|
}
|
|
/*
|
* Record a quiescent state for the specified CPU to that CPU's rcu_data
|
* structure. This must be called from the specified CPU.
|
*/
|
static void
|
rcu_report_qs_rdp(struct rcu_data *rdp)
|
{
|
unsigned long flags;
|
unsigned long mask;
|
bool needwake = false;
|
const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
|
rcu_segcblist_is_offloaded(&rdp->cblist);
|
struct rcu_node *rnp;
|
|
WARN_ON_ONCE(rdp->cpu != smp_processor_id());
|
rnp = rdp->mynode;
|
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
if (rdp->cpu_no_qs.b.norm || rdp->gp_seq != rnp->gp_seq ||
|
rdp->gpwrap) {
|
|
/*
|
* The grace period in which this quiescent state was
|
* recorded has ended, so don't report it upwards.
|
* We will instead need a new quiescent state that lies
|
* within the current grace period.
|
*/
|
rdp->cpu_no_qs.b.norm = true; /* need qs for new gp. */
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
return;
|
}
|
mask = rdp->grpmask;
|
rdp->core_needs_qs = false;
|
if ((rnp->qsmask & mask) == 0) {
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
} else {
|
/*
|
* This GP can't end until cpu checks in, so all of our
|
* callbacks can be processed during the next GP.
|
*/
|
if (!offloaded)
|
needwake = rcu_accelerate_cbs(rnp, rdp);
|
|
rcu_disable_urgency_upon_qs(rdp);
|
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
|
/* ^^^ Released rnp->lock */
|
if (needwake)
|
rcu_gp_kthread_wake();
|
}
|
}
|
|
/*
|
* Check to see if there is a new grace period of which this CPU
|
* is not yet aware, and if so, set up local rcu_data state for it.
|
* Otherwise, see if this CPU has just passed through its first
|
* quiescent state for this grace period, and record that fact if so.
|
*/
|
static void
|
rcu_check_quiescent_state(struct rcu_data *rdp)
|
{
|
/* Check for grace-period ends and beginnings. */
|
note_gp_changes(rdp);
|
|
/*
|
* Does this CPU still need to do its part for current grace period?
|
* If no, return and let the other CPUs do their part as well.
|
*/
|
if (!rdp->core_needs_qs)
|
return;
|
|
/*
|
* Was there a quiescent state since the beginning of the grace
|
* period? If no, then exit and wait for the next call.
|
*/
|
if (rdp->cpu_no_qs.b.norm)
|
return;
|
|
/*
|
* Tell RCU we are done (but rcu_report_qs_rdp() will be the
|
* judge of that).
|
*/
|
rcu_report_qs_rdp(rdp);
|
}
|
|
/*
|
* Near the end of the offline process. Trace the fact that this CPU
|
* is going offline.
|
*/
|
int rcutree_dying_cpu(unsigned int cpu)
|
{
|
bool blkd;
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
struct rcu_node *rnp = rdp->mynode;
|
|
if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
|
return 0;
|
|
blkd = !!(rnp->qsmask & rdp->grpmask);
|
trace_rcu_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq),
|
blkd ? TPS("cpuofl") : TPS("cpuofl-bgp"));
|
return 0;
|
}
|
|
/*
|
* All CPUs for the specified rcu_node structure have gone offline,
|
* and all tasks that were preempted within an RCU read-side critical
|
* section while running on one of those CPUs have since exited their RCU
|
* read-side critical section. Some other CPU is reporting this fact with
|
* the specified rcu_node structure's ->lock held and interrupts disabled.
|
* This function therefore goes up the tree of rcu_node structures,
|
* clearing the corresponding bits in the ->qsmaskinit fields. Note that
|
* the leaf rcu_node structure's ->qsmaskinit field has already been
|
* updated.
|
*
|
* This function does check that the specified rcu_node structure has
|
* all CPUs offline and no blocked tasks, so it is OK to invoke it
|
* prematurely. That said, invoking it after the fact will cost you
|
* a needless lock acquisition. So once it has done its work, don't
|
* invoke it again.
|
*/
|
static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
|
{
|
long mask;
|
struct rcu_node *rnp = rnp_leaf;
|
|
raw_lockdep_assert_held_rcu_node(rnp_leaf);
|
if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) ||
|
WARN_ON_ONCE(rnp_leaf->qsmaskinit) ||
|
WARN_ON_ONCE(rcu_preempt_has_tasks(rnp_leaf)))
|
return;
|
for (;;) {
|
mask = rnp->grpmask;
|
rnp = rnp->parent;
|
if (!rnp)
|
break;
|
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
|
rnp->qsmaskinit &= ~mask;
|
/* Between grace periods, so better already be zero! */
|
WARN_ON_ONCE(rnp->qsmask);
|
if (rnp->qsmaskinit) {
|
raw_spin_unlock_rcu_node(rnp);
|
/* irqs remain disabled. */
|
return;
|
}
|
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
|
}
|
}
|
|
/*
|
* The CPU has been completely removed, and some other CPU is reporting
|
* this fact from process context. Do the remainder of the cleanup.
|
* There can only be one CPU hotplug operation at a time, so no need for
|
* explicit locking.
|
*/
|
int rcutree_dead_cpu(unsigned int cpu)
|
{
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
|
|
if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
|
return 0;
|
|
/* Adjust any no-longer-needed kthreads. */
|
rcu_boost_kthread_setaffinity(rnp, -1);
|
/* Do any needed no-CB deferred wakeups from this CPU. */
|
do_nocb_deferred_wakeup(per_cpu_ptr(&rcu_data, cpu));
|
|
// Stop-machine done, so allow nohz_full to disable tick.
|
tick_dep_clear(TICK_DEP_BIT_RCU);
|
return 0;
|
}
|
|
/*
|
* Invoke any RCU callbacks that have made it to the end of their grace
|
* period. Thottle as specified by rdp->blimit.
|
*/
|
static void rcu_do_batch(struct rcu_data *rdp)
|
{
|
int div;
|
unsigned long flags;
|
const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
|
rcu_segcblist_is_offloaded(&rdp->cblist);
|
struct rcu_head *rhp;
|
struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl);
|
long bl, count;
|
long pending, tlimit = 0;
|
|
/* If no callbacks are ready, just return. */
|
if (!rcu_segcblist_ready_cbs(&rdp->cblist)) {
|
trace_rcu_batch_start(rcu_state.name,
|
rcu_segcblist_n_cbs(&rdp->cblist), 0);
|
trace_rcu_batch_end(rcu_state.name, 0,
|
!rcu_segcblist_empty(&rdp->cblist),
|
need_resched(), is_idle_task(current),
|
rcu_is_callbacks_kthread());
|
return;
|
}
|
|
/*
|
* Extract the list of ready callbacks, disabling to prevent
|
* races with call_rcu() from interrupt handlers. Leave the
|
* callback counts, as rcu_barrier() needs to be conservative.
|
*/
|
local_irq_save(flags);
|
rcu_nocb_lock(rdp);
|
WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
|
pending = rcu_segcblist_n_cbs(&rdp->cblist);
|
div = READ_ONCE(rcu_divisor);
|
div = div < 0 ? 7 : div > sizeof(long) * 8 - 2 ? sizeof(long) * 8 - 2 : div;
|
bl = max(rdp->blimit, pending >> div);
|
if (in_serving_softirq() && unlikely(bl > 100)) {
|
long rrn = READ_ONCE(rcu_resched_ns);
|
|
rrn = rrn < NSEC_PER_MSEC ? NSEC_PER_MSEC : rrn > NSEC_PER_SEC ? NSEC_PER_SEC : rrn;
|
tlimit = local_clock() + rrn;
|
}
|
trace_rcu_batch_start(rcu_state.name,
|
rcu_segcblist_n_cbs(&rdp->cblist), bl);
|
rcu_segcblist_extract_done_cbs(&rdp->cblist, &rcl);
|
if (offloaded)
|
rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist);
|
rcu_nocb_unlock_irqrestore(rdp, flags);
|
|
/* Invoke callbacks. */
|
tick_dep_set_task(current, TICK_DEP_BIT_RCU);
|
rhp = rcu_cblist_dequeue(&rcl);
|
for (; rhp; rhp = rcu_cblist_dequeue(&rcl)) {
|
rcu_callback_t f;
|
|
debug_rcu_head_unqueue(rhp);
|
|
rcu_lock_acquire(&rcu_callback_map);
|
trace_rcu_invoke_callback(rcu_state.name, rhp);
|
|
f = rhp->func;
|
WRITE_ONCE(rhp->func, (rcu_callback_t)0L);
|
f(rhp);
|
|
rcu_lock_release(&rcu_callback_map);
|
|
/*
|
* Stop only if limit reached and CPU has something to do.
|
* Note: The rcl structure counts down from zero.
|
*/
|
if (in_serving_softirq()) {
|
if (-rcl.len >= bl && (need_resched() ||
|
(!is_idle_task(current) && !rcu_is_callbacks_kthread())))
|
break;
|
|
/*
|
* Make sure we don't spend too much time here and deprive other
|
* softirq vectors of CPU cycles.
|
*/
|
if (unlikely(tlimit)) {
|
/* only call local_clock() every 32 callbacks */
|
if (likely((-rcl.len & 31) || local_clock() < tlimit))
|
continue;
|
/* Exceeded the time limit, so leave. */
|
break;
|
}
|
} else {
|
local_bh_enable();
|
lockdep_assert_irqs_enabled();
|
cond_resched_tasks_rcu_qs();
|
lockdep_assert_irqs_enabled();
|
local_bh_disable();
|
}
|
}
|
|
local_irq_save(flags);
|
rcu_nocb_lock(rdp);
|
count = -rcl.len;
|
rdp->n_cbs_invoked += count;
|
trace_rcu_batch_end(rcu_state.name, count, !!rcl.head, need_resched(),
|
is_idle_task(current), rcu_is_callbacks_kthread());
|
|
/* Update counts and requeue any remaining callbacks. */
|
rcu_segcblist_insert_done_cbs(&rdp->cblist, &rcl);
|
smp_mb(); /* List handling before counting for rcu_barrier(). */
|
rcu_segcblist_insert_count(&rdp->cblist, &rcl);
|
|
/* Reinstate batch limit if we have worked down the excess. */
|
count = rcu_segcblist_n_cbs(&rdp->cblist);
|
if (rdp->blimit >= DEFAULT_MAX_RCU_BLIMIT && count <= qlowmark)
|
rdp->blimit = blimit;
|
|
/* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
|
if (count == 0 && rdp->qlen_last_fqs_check != 0) {
|
rdp->qlen_last_fqs_check = 0;
|
rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
|
} else if (count < rdp->qlen_last_fqs_check - qhimark)
|
rdp->qlen_last_fqs_check = count;
|
|
/*
|
* The following usually indicates a double call_rcu(). To track
|
* this down, try building with CONFIG_DEBUG_OBJECTS_RCU_HEAD=y.
|
*/
|
WARN_ON_ONCE(count == 0 && !rcu_segcblist_empty(&rdp->cblist));
|
WARN_ON_ONCE(!IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
|
count != 0 && rcu_segcblist_empty(&rdp->cblist));
|
|
rcu_nocb_unlock_irqrestore(rdp, flags);
|
|
/* Re-invoke RCU core processing if there are callbacks remaining. */
|
if (!offloaded && rcu_segcblist_ready_cbs(&rdp->cblist))
|
invoke_rcu_core();
|
tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
|
}
|
|
/*
|
* This function is invoked from each scheduling-clock interrupt,
|
* and checks to see if this CPU is in a non-context-switch quiescent
|
* state, for example, user mode or idle loop. It also schedules RCU
|
* core processing. If the current grace period has gone on too long,
|
* it will ask the scheduler to manufacture a context switch for the sole
|
* purpose of providing a providing the needed quiescent state.
|
*/
|
void rcu_sched_clock_irq(int user)
|
{
|
trace_rcu_utilization(TPS("Start scheduler-tick"));
|
lockdep_assert_irqs_disabled();
|
raw_cpu_inc(rcu_data.ticks_this_gp);
|
/* The load-acquire pairs with the store-release setting to true. */
|
if (smp_load_acquire(this_cpu_ptr(&rcu_data.rcu_urgent_qs))) {
|
/* Idle and userspace execution already are quiescent states. */
|
if (!rcu_is_cpu_rrupt_from_idle() && !user) {
|
set_tsk_need_resched(current);
|
set_preempt_need_resched();
|
}
|
__this_cpu_write(rcu_data.rcu_urgent_qs, false);
|
}
|
rcu_flavor_sched_clock_irq(user);
|
if (rcu_pending(user))
|
invoke_rcu_core();
|
lockdep_assert_irqs_disabled();
|
|
trace_rcu_utilization(TPS("End scheduler-tick"));
|
}
|
|
/*
|
* Scan the leaf rcu_node structures. For each structure on which all
|
* CPUs have reported a quiescent state and on which there are tasks
|
* blocking the current grace period, initiate RCU priority boosting.
|
* Otherwise, invoke the specified function to check dyntick state for
|
* each CPU that has not yet reported a quiescent state.
|
*/
|
static void force_qs_rnp(int (*f)(struct rcu_data *rdp))
|
{
|
int cpu;
|
unsigned long flags;
|
unsigned long mask;
|
struct rcu_data *rdp;
|
struct rcu_node *rnp;
|
|
rcu_state.cbovld = rcu_state.cbovldnext;
|
rcu_state.cbovldnext = false;
|
rcu_for_each_leaf_node(rnp) {
|
cond_resched_tasks_rcu_qs();
|
mask = 0;
|
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
rcu_state.cbovldnext |= !!rnp->cbovldmask;
|
if (rnp->qsmask == 0) {
|
if (rcu_preempt_blocked_readers_cgp(rnp)) {
|
/*
|
* No point in scanning bits because they
|
* are all zero. But we might need to
|
* priority-boost blocked readers.
|
*/
|
rcu_initiate_boost(rnp, flags);
|
/* rcu_initiate_boost() releases rnp->lock */
|
continue;
|
}
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
continue;
|
}
|
for_each_leaf_node_cpu_mask(rnp, cpu, rnp->qsmask) {
|
rdp = per_cpu_ptr(&rcu_data, cpu);
|
if (f(rdp)) {
|
mask |= rdp->grpmask;
|
rcu_disable_urgency_upon_qs(rdp);
|
}
|
}
|
if (mask != 0) {
|
/* Idle/offline CPUs, report (releases rnp->lock). */
|
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
|
} else {
|
/* Nothing to do here, so just drop the lock. */
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
}
|
}
|
}
|
|
/*
|
* Force quiescent states on reluctant CPUs, and also detect which
|
* CPUs are in dyntick-idle mode.
|
*/
|
void rcu_force_quiescent_state(void)
|
{
|
unsigned long flags;
|
bool ret;
|
struct rcu_node *rnp;
|
struct rcu_node *rnp_old = NULL;
|
|
/* Funnel through hierarchy to reduce memory contention. */
|
rnp = __this_cpu_read(rcu_data.mynode);
|
for (; rnp != NULL; rnp = rnp->parent) {
|
ret = (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) ||
|
!raw_spin_trylock(&rnp->fqslock);
|
if (rnp_old != NULL)
|
raw_spin_unlock(&rnp_old->fqslock);
|
if (ret)
|
return;
|
rnp_old = rnp;
|
}
|
/* rnp_old == rcu_get_root(), rnp == NULL. */
|
|
/* Reached the root of the rcu_node tree, acquire lock. */
|
raw_spin_lock_irqsave_rcu_node(rnp_old, flags);
|
raw_spin_unlock(&rnp_old->fqslock);
|
if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) {
|
raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags);
|
return; /* Someone beat us to it. */
|
}
|
WRITE_ONCE(rcu_state.gp_flags,
|
READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS);
|
raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags);
|
rcu_gp_kthread_wake();
|
}
|
EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
|
|
// Workqueue handler for an RCU reader for kernels enforcing struct RCU
|
// grace periods.
|
static void strict_work_handler(struct work_struct *work)
|
{
|
rcu_read_lock();
|
rcu_read_unlock();
|
}
|
|
/* Perform RCU core processing work for the current CPU. */
|
static __latent_entropy void rcu_core(void)
|
{
|
unsigned long flags;
|
struct rcu_data *rdp = raw_cpu_ptr(&rcu_data);
|
struct rcu_node *rnp = rdp->mynode;
|
const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
|
rcu_segcblist_is_offloaded(&rdp->cblist);
|
|
if (cpu_is_offline(smp_processor_id()))
|
return;
|
trace_rcu_utilization(TPS("Start RCU core"));
|
WARN_ON_ONCE(!rdp->beenonline);
|
|
/* Report any deferred quiescent states if preemption enabled. */
|
if (!(preempt_count() & PREEMPT_MASK)) {
|
rcu_preempt_deferred_qs(current);
|
} else if (rcu_preempt_need_deferred_qs(current)) {
|
set_tsk_need_resched(current);
|
set_preempt_need_resched();
|
}
|
|
/* Update RCU state based on any recent quiescent states. */
|
rcu_check_quiescent_state(rdp);
|
|
/* No grace period and unregistered callbacks? */
|
if (!rcu_gp_in_progress() &&
|
rcu_segcblist_is_enabled(&rdp->cblist) && !offloaded) {
|
local_irq_save(flags);
|
if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
|
rcu_accelerate_cbs_unlocked(rnp, rdp);
|
local_irq_restore(flags);
|
}
|
|
rcu_check_gp_start_stall(rnp, rdp, rcu_jiffies_till_stall_check());
|
|
/* If there are callbacks ready, invoke them. */
|
if (!offloaded && rcu_segcblist_ready_cbs(&rdp->cblist) &&
|
likely(READ_ONCE(rcu_scheduler_fully_active)))
|
rcu_do_batch(rdp);
|
|
/* Do any needed deferred wakeups of rcuo kthreads. */
|
do_nocb_deferred_wakeup(rdp);
|
trace_rcu_utilization(TPS("End RCU core"));
|
|
// If strict GPs, schedule an RCU reader in a clean environment.
|
if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
|
queue_work_on(rdp->cpu, rcu_gp_wq, &rdp->strict_work);
|
}
|
|
static void rcu_core_si(struct softirq_action *h)
|
{
|
rcu_core();
|
}
|
|
static void rcu_wake_cond(struct task_struct *t, int status)
|
{
|
/*
|
* If the thread is yielding, only wake it when this
|
* is invoked from idle
|
*/
|
if (t && (status != RCU_KTHREAD_YIELDING || is_idle_task(current)))
|
wake_up_process(t);
|
}
|
|
static void invoke_rcu_core_kthread(void)
|
{
|
struct task_struct *t;
|
unsigned long flags;
|
|
local_irq_save(flags);
|
__this_cpu_write(rcu_data.rcu_cpu_has_work, 1);
|
t = __this_cpu_read(rcu_data.rcu_cpu_kthread_task);
|
if (t != NULL && t != current)
|
rcu_wake_cond(t, __this_cpu_read(rcu_data.rcu_cpu_kthread_status));
|
local_irq_restore(flags);
|
}
|
|
/*
|
* Wake up this CPU's rcuc kthread to do RCU core processing.
|
*/
|
static void invoke_rcu_core(void)
|
{
|
if (!cpu_online(smp_processor_id()))
|
return;
|
if (use_softirq)
|
raise_softirq(RCU_SOFTIRQ);
|
else
|
invoke_rcu_core_kthread();
|
}
|
|
static void rcu_cpu_kthread_park(unsigned int cpu)
|
{
|
per_cpu(rcu_data.rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU;
|
}
|
|
static int rcu_cpu_kthread_should_run(unsigned int cpu)
|
{
|
return __this_cpu_read(rcu_data.rcu_cpu_has_work);
|
}
|
|
/*
|
* Per-CPU kernel thread that invokes RCU callbacks. This replaces
|
* the RCU softirq used in configurations of RCU that do not support RCU
|
* priority boosting.
|
*/
|
static void rcu_cpu_kthread(unsigned int cpu)
|
{
|
unsigned int *statusp = this_cpu_ptr(&rcu_data.rcu_cpu_kthread_status);
|
char work, *workp = this_cpu_ptr(&rcu_data.rcu_cpu_has_work);
|
int spincnt;
|
|
trace_rcu_utilization(TPS("Start CPU kthread@rcu_run"));
|
for (spincnt = 0; spincnt < 10; spincnt++) {
|
local_bh_disable();
|
*statusp = RCU_KTHREAD_RUNNING;
|
local_irq_disable();
|
work = *workp;
|
*workp = 0;
|
local_irq_enable();
|
if (work)
|
rcu_core();
|
local_bh_enable();
|
if (*workp == 0) {
|
trace_rcu_utilization(TPS("End CPU kthread@rcu_wait"));
|
*statusp = RCU_KTHREAD_WAITING;
|
return;
|
}
|
}
|
*statusp = RCU_KTHREAD_YIELDING;
|
trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield"));
|
schedule_timeout_idle(2);
|
trace_rcu_utilization(TPS("End CPU kthread@rcu_yield"));
|
*statusp = RCU_KTHREAD_WAITING;
|
}
|
|
static struct smp_hotplug_thread rcu_cpu_thread_spec = {
|
.store = &rcu_data.rcu_cpu_kthread_task,
|
.thread_should_run = rcu_cpu_kthread_should_run,
|
.thread_fn = rcu_cpu_kthread,
|
.thread_comm = "rcuc/%u",
|
.setup = rcu_cpu_kthread_setup,
|
.park = rcu_cpu_kthread_park,
|
};
|
|
/*
|
* Spawn per-CPU RCU core processing kthreads.
|
*/
|
static int __init rcu_spawn_core_kthreads(void)
|
{
|
int cpu;
|
|
for_each_possible_cpu(cpu)
|
per_cpu(rcu_data.rcu_cpu_has_work, cpu) = 0;
|
if (!IS_ENABLED(CONFIG_RCU_BOOST) && use_softirq)
|
return 0;
|
WARN_ONCE(smpboot_register_percpu_thread(&rcu_cpu_thread_spec),
|
"%s: Could not start rcuc kthread, OOM is now expected behavior\n", __func__);
|
return 0;
|
}
|
|
/*
|
* Handle any core-RCU processing required by a call_rcu() invocation.
|
*/
|
static void __call_rcu_core(struct rcu_data *rdp, struct rcu_head *head,
|
unsigned long flags)
|
{
|
/*
|
* If called from an extended quiescent state, invoke the RCU
|
* core in order to force a re-evaluation of RCU's idleness.
|
*/
|
if (!rcu_is_watching())
|
invoke_rcu_core();
|
|
/* If interrupts were disabled or CPU offline, don't invoke RCU core. */
|
if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id()))
|
return;
|
|
/*
|
* Force the grace period if too many callbacks or too long waiting.
|
* Enforce hysteresis, and don't invoke rcu_force_quiescent_state()
|
* if some other CPU has recently done so. Also, don't bother
|
* invoking rcu_force_quiescent_state() if the newly enqueued callback
|
* is the only one waiting for a grace period to complete.
|
*/
|
if (unlikely(rcu_segcblist_n_cbs(&rdp->cblist) >
|
rdp->qlen_last_fqs_check + qhimark)) {
|
|
/* Are we ignoring a completed grace period? */
|
note_gp_changes(rdp);
|
|
/* Start a new grace period if one not already started. */
|
if (!rcu_gp_in_progress()) {
|
rcu_accelerate_cbs_unlocked(rdp->mynode, rdp);
|
} else {
|
/* Give the grace period a kick. */
|
rdp->blimit = DEFAULT_MAX_RCU_BLIMIT;
|
if (READ_ONCE(rcu_state.n_force_qs) == rdp->n_force_qs_snap &&
|
rcu_segcblist_first_pend_cb(&rdp->cblist) != head)
|
rcu_force_quiescent_state();
|
rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
|
rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist);
|
}
|
}
|
}
|
|
/*
|
* RCU callback function to leak a callback.
|
*/
|
static void rcu_leak_callback(struct rcu_head *rhp)
|
{
|
}
|
|
/*
|
* Check and if necessary update the leaf rcu_node structure's
|
* ->cbovldmask bit corresponding to the current CPU based on that CPU's
|
* number of queued RCU callbacks. The caller must hold the leaf rcu_node
|
* structure's ->lock.
|
*/
|
static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp)
|
{
|
raw_lockdep_assert_held_rcu_node(rnp);
|
if (qovld_calc <= 0)
|
return; // Early boot and wildcard value set.
|
if (rcu_segcblist_n_cbs(&rdp->cblist) >= qovld_calc)
|
WRITE_ONCE(rnp->cbovldmask, rnp->cbovldmask | rdp->grpmask);
|
else
|
WRITE_ONCE(rnp->cbovldmask, rnp->cbovldmask & ~rdp->grpmask);
|
}
|
|
/*
|
* Check and if necessary update the leaf rcu_node structure's
|
* ->cbovldmask bit corresponding to the current CPU based on that CPU's
|
* number of queued RCU callbacks. No locks need be held, but the
|
* caller must have disabled interrupts.
|
*
|
* Note that this function ignores the possibility that there are a lot
|
* of callbacks all of which have already seen the end of their respective
|
* grace periods. This omission is due to the need for no-CBs CPUs to
|
* be holding ->nocb_lock to do this check, which is too heavy for a
|
* common-case operation.
|
*/
|
static void check_cb_ovld(struct rcu_data *rdp)
|
{
|
struct rcu_node *const rnp = rdp->mynode;
|
|
if (qovld_calc <= 0 ||
|
((rcu_segcblist_n_cbs(&rdp->cblist) >= qovld_calc) ==
|
!!(READ_ONCE(rnp->cbovldmask) & rdp->grpmask)))
|
return; // Early boot wildcard value or already set correctly.
|
raw_spin_lock_rcu_node(rnp);
|
check_cb_ovld_locked(rdp, rnp);
|
raw_spin_unlock_rcu_node(rnp);
|
}
|
|
/* Helper function for call_rcu() and friends. */
|
static void
|
__call_rcu(struct rcu_head *head, rcu_callback_t func)
|
{
|
unsigned long flags;
|
struct rcu_data *rdp;
|
bool was_alldone;
|
|
/* Misaligned rcu_head! */
|
WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1));
|
|
if (debug_rcu_head_queue(head)) {
|
/*
|
* Probable double call_rcu(), so leak the callback.
|
* Use rcu:rcu_callback trace event to find the previous
|
* time callback was passed to __call_rcu().
|
*/
|
WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pS()!!!\n",
|
head, head->func);
|
WRITE_ONCE(head->func, rcu_leak_callback);
|
return;
|
}
|
head->func = func;
|
head->next = NULL;
|
local_irq_save(flags);
|
kasan_record_aux_stack(head);
|
rdp = this_cpu_ptr(&rcu_data);
|
|
/* Add the callback to our list. */
|
if (unlikely(!rcu_segcblist_is_enabled(&rdp->cblist))) {
|
// This can trigger due to call_rcu() from offline CPU:
|
WARN_ON_ONCE(rcu_scheduler_active != RCU_SCHEDULER_INACTIVE);
|
WARN_ON_ONCE(!rcu_is_watching());
|
// Very early boot, before rcu_init(). Initialize if needed
|
// and then drop through to queue the callback.
|
if (rcu_segcblist_empty(&rdp->cblist))
|
rcu_segcblist_init(&rdp->cblist);
|
}
|
|
check_cb_ovld(rdp);
|
if (rcu_nocb_try_bypass(rdp, head, &was_alldone, flags))
|
return; // Enqueued onto ->nocb_bypass, so just leave.
|
// If no-CBs CPU gets here, rcu_nocb_try_bypass() acquired ->nocb_lock.
|
rcu_segcblist_enqueue(&rdp->cblist, head);
|
if (__is_kvfree_rcu_offset((unsigned long)func))
|
trace_rcu_kvfree_callback(rcu_state.name, head,
|
(unsigned long)func,
|
rcu_segcblist_n_cbs(&rdp->cblist));
|
else
|
trace_rcu_callback(rcu_state.name, head,
|
rcu_segcblist_n_cbs(&rdp->cblist));
|
|
/* Go handle any RCU core processing required. */
|
if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
|
unlikely(rcu_segcblist_is_offloaded(&rdp->cblist))) {
|
__call_rcu_nocb_wake(rdp, was_alldone, flags); /* unlocks */
|
} else {
|
__call_rcu_core(rdp, head, flags);
|
local_irq_restore(flags);
|
}
|
}
|
|
/**
|
* call_rcu() - Queue an RCU callback for invocation after a grace period.
|
* @head: structure to be used for queueing the RCU updates.
|
* @func: actual callback function to be invoked after the grace period
|
*
|
* The callback function will be invoked some time after a full grace
|
* period elapses, in other words after all pre-existing RCU read-side
|
* critical sections have completed. However, the callback function
|
* might well execute concurrently with RCU read-side critical sections
|
* that started after call_rcu() was invoked. RCU read-side critical
|
* sections are delimited by rcu_read_lock() and rcu_read_unlock(), and
|
* may be nested. In addition, regions of code across which interrupts,
|
* preemption, or softirqs have been disabled also serve as RCU read-side
|
* critical sections. This includes hardware interrupt handlers, softirq
|
* handlers, and NMI handlers.
|
*
|
* Note that all CPUs must agree that the grace period extended beyond
|
* all pre-existing RCU read-side critical section. On systems with more
|
* than one CPU, this means that when "func()" is invoked, each CPU is
|
* guaranteed to have executed a full memory barrier since the end of its
|
* last RCU read-side critical section whose beginning preceded the call
|
* to call_rcu(). It also means that each CPU executing an RCU read-side
|
* critical section that continues beyond the start of "func()" must have
|
* executed a memory barrier after the call_rcu() but before the beginning
|
* of that RCU read-side critical section. Note that these guarantees
|
* include CPUs that are offline, idle, or executing in user mode, as
|
* well as CPUs that are executing in the kernel.
|
*
|
* Furthermore, if CPU A invoked call_rcu() and CPU B invoked the
|
* resulting RCU callback function "func()", then both CPU A and CPU B are
|
* guaranteed to execute a full memory barrier during the time interval
|
* between the call to call_rcu() and the invocation of "func()" -- even
|
* if CPU A and CPU B are the same CPU (but again only if the system has
|
* more than one CPU).
|
*/
|
void call_rcu(struct rcu_head *head, rcu_callback_t func)
|
{
|
__call_rcu(head, func);
|
}
|
EXPORT_SYMBOL_GPL(call_rcu);
|
|
|
/* Maximum number of jiffies to wait before draining a batch. */
|
#define KFREE_DRAIN_JIFFIES (HZ / 50)
|
#define KFREE_N_BATCHES 2
|
#define FREE_N_CHANNELS 2
|
|
/**
|
* struct kvfree_rcu_bulk_data - single block to store kvfree_rcu() pointers
|
* @nr_records: Number of active pointers in the array
|
* @next: Next bulk object in the block chain
|
* @records: Array of the kvfree_rcu() pointers
|
*/
|
struct kvfree_rcu_bulk_data {
|
unsigned long nr_records;
|
struct kvfree_rcu_bulk_data *next;
|
void *records[];
|
};
|
|
/*
|
* This macro defines how many entries the "records" array
|
* will contain. It is based on the fact that the size of
|
* kvfree_rcu_bulk_data structure becomes exactly one page.
|
*/
|
#define KVFREE_BULK_MAX_ENTR \
|
((PAGE_SIZE - sizeof(struct kvfree_rcu_bulk_data)) / sizeof(void *))
|
|
/**
|
* struct kfree_rcu_cpu_work - single batch of kfree_rcu() requests
|
* @rcu_work: Let queue_rcu_work() invoke workqueue handler after grace period
|
* @head_free: List of kfree_rcu() objects waiting for a grace period
|
* @bkvhead_free: Bulk-List of kvfree_rcu() objects waiting for a grace period
|
* @krcp: Pointer to @kfree_rcu_cpu structure
|
*/
|
|
struct kfree_rcu_cpu_work {
|
struct rcu_work rcu_work;
|
struct rcu_head *head_free;
|
struct kvfree_rcu_bulk_data *bkvhead_free[FREE_N_CHANNELS];
|
struct kfree_rcu_cpu *krcp;
|
};
|
|
/**
|
* struct kfree_rcu_cpu - batch up kfree_rcu() requests for RCU grace period
|
* @head: List of kfree_rcu() objects not yet waiting for a grace period
|
* @bkvhead: Bulk-List of kvfree_rcu() objects not yet waiting for a grace period
|
* @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period
|
* @lock: Synchronize access to this structure
|
* @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES
|
* @monitor_todo: Tracks whether a @monitor_work delayed work is pending
|
* @initialized: The @rcu_work fields have been initialized
|
* @count: Number of objects for which GP not started
|
* @bkvcache:
|
* A simple cache list that contains objects for reuse purpose.
|
* In order to save some per-cpu space the list is singular.
|
* Even though it is lockless an access has to be protected by the
|
* per-cpu lock.
|
* @page_cache_work: A work to refill the cache when it is empty
|
* @work_in_progress: Indicates that page_cache_work is running
|
* @hrtimer: A hrtimer for scheduling a page_cache_work
|
* @nr_bkv_objs: number of allocated objects at @bkvcache.
|
*
|
* This is a per-CPU structure. The reason that it is not included in
|
* the rcu_data structure is to permit this code to be extracted from
|
* the RCU files. Such extraction could allow further optimization of
|
* the interactions with the slab allocators.
|
*/
|
struct kfree_rcu_cpu {
|
struct rcu_head *head;
|
struct kvfree_rcu_bulk_data *bkvhead[FREE_N_CHANNELS];
|
struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES];
|
raw_spinlock_t lock;
|
struct delayed_work monitor_work;
|
bool monitor_todo;
|
bool initialized;
|
int count;
|
|
struct work_struct page_cache_work;
|
atomic_t work_in_progress;
|
struct hrtimer hrtimer;
|
|
struct llist_head bkvcache;
|
int nr_bkv_objs;
|
};
|
|
static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc) = {
|
.lock = __RAW_SPIN_LOCK_UNLOCKED(krc.lock),
|
};
|
|
static __always_inline void
|
debug_rcu_bhead_unqueue(struct kvfree_rcu_bulk_data *bhead)
|
{
|
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
|
int i;
|
|
for (i = 0; i < bhead->nr_records; i++)
|
debug_rcu_head_unqueue((struct rcu_head *)(bhead->records[i]));
|
#endif
|
}
|
|
static inline struct kfree_rcu_cpu *
|
krc_this_cpu_lock(unsigned long *flags)
|
{
|
struct kfree_rcu_cpu *krcp;
|
|
local_irq_save(*flags); // For safely calling this_cpu_ptr().
|
krcp = this_cpu_ptr(&krc);
|
raw_spin_lock(&krcp->lock);
|
|
return krcp;
|
}
|
|
static inline void
|
krc_this_cpu_unlock(struct kfree_rcu_cpu *krcp, unsigned long flags)
|
{
|
raw_spin_unlock(&krcp->lock);
|
local_irq_restore(flags);
|
}
|
|
static inline struct kvfree_rcu_bulk_data *
|
get_cached_bnode(struct kfree_rcu_cpu *krcp)
|
{
|
if (!krcp->nr_bkv_objs)
|
return NULL;
|
|
krcp->nr_bkv_objs--;
|
return (struct kvfree_rcu_bulk_data *)
|
llist_del_first(&krcp->bkvcache);
|
}
|
|
static inline bool
|
put_cached_bnode(struct kfree_rcu_cpu *krcp,
|
struct kvfree_rcu_bulk_data *bnode)
|
{
|
// Check the limit.
|
if (krcp->nr_bkv_objs >= rcu_min_cached_objs)
|
return false;
|
|
llist_add((struct llist_node *) bnode, &krcp->bkvcache);
|
krcp->nr_bkv_objs++;
|
return true;
|
|
}
|
|
/*
|
* This function is invoked in workqueue context after a grace period.
|
* It frees all the objects queued on ->bhead_free or ->head_free.
|
*/
|
static void kfree_rcu_work(struct work_struct *work)
|
{
|
unsigned long flags;
|
struct kvfree_rcu_bulk_data *bkvhead[FREE_N_CHANNELS], *bnext;
|
struct rcu_head *head, *next;
|
struct kfree_rcu_cpu *krcp;
|
struct kfree_rcu_cpu_work *krwp;
|
int i, j;
|
|
krwp = container_of(to_rcu_work(work),
|
struct kfree_rcu_cpu_work, rcu_work);
|
krcp = krwp->krcp;
|
|
raw_spin_lock_irqsave(&krcp->lock, flags);
|
// Channels 1 and 2.
|
for (i = 0; i < FREE_N_CHANNELS; i++) {
|
bkvhead[i] = krwp->bkvhead_free[i];
|
krwp->bkvhead_free[i] = NULL;
|
}
|
|
// Channel 3.
|
head = krwp->head_free;
|
krwp->head_free = NULL;
|
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
|
// Handle two first channels.
|
for (i = 0; i < FREE_N_CHANNELS; i++) {
|
for (; bkvhead[i]; bkvhead[i] = bnext) {
|
bnext = bkvhead[i]->next;
|
debug_rcu_bhead_unqueue(bkvhead[i]);
|
|
rcu_lock_acquire(&rcu_callback_map);
|
if (i == 0) { // kmalloc() / kfree().
|
trace_rcu_invoke_kfree_bulk_callback(
|
rcu_state.name, bkvhead[i]->nr_records,
|
bkvhead[i]->records);
|
|
kfree_bulk(bkvhead[i]->nr_records,
|
bkvhead[i]->records);
|
} else { // vmalloc() / vfree().
|
for (j = 0; j < bkvhead[i]->nr_records; j++) {
|
trace_rcu_invoke_kvfree_callback(
|
rcu_state.name,
|
bkvhead[i]->records[j], 0);
|
|
vfree(bkvhead[i]->records[j]);
|
}
|
}
|
rcu_lock_release(&rcu_callback_map);
|
|
raw_spin_lock_irqsave(&krcp->lock, flags);
|
if (put_cached_bnode(krcp, bkvhead[i]))
|
bkvhead[i] = NULL;
|
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
|
if (bkvhead[i])
|
free_page((unsigned long) bkvhead[i]);
|
|
cond_resched_tasks_rcu_qs();
|
}
|
}
|
|
/*
|
* Emergency case only. It can happen under low memory
|
* condition when an allocation gets failed, so the "bulk"
|
* path can not be temporary maintained.
|
*/
|
for (; head; head = next) {
|
unsigned long offset = (unsigned long)head->func;
|
void *ptr = (void *)head - offset;
|
|
next = head->next;
|
debug_rcu_head_unqueue((struct rcu_head *)ptr);
|
rcu_lock_acquire(&rcu_callback_map);
|
trace_rcu_invoke_kvfree_callback(rcu_state.name, head, offset);
|
|
if (!WARN_ON_ONCE(!__is_kvfree_rcu_offset(offset)))
|
kvfree(ptr);
|
|
rcu_lock_release(&rcu_callback_map);
|
cond_resched_tasks_rcu_qs();
|
}
|
}
|
|
/*
|
* Schedule the kfree batch RCU work to run in workqueue context after a GP.
|
*
|
* This function is invoked by kfree_rcu_monitor() when the KFREE_DRAIN_JIFFIES
|
* timeout has been reached.
|
*/
|
static inline bool queue_kfree_rcu_work(struct kfree_rcu_cpu *krcp)
|
{
|
struct kfree_rcu_cpu_work *krwp;
|
bool repeat = false;
|
int i, j;
|
|
lockdep_assert_held(&krcp->lock);
|
|
for (i = 0; i < KFREE_N_BATCHES; i++) {
|
krwp = &(krcp->krw_arr[i]);
|
|
/*
|
* Try to detach bkvhead or head and attach it over any
|
* available corresponding free channel. It can be that
|
* a previous RCU batch is in progress, it means that
|
* immediately to queue another one is not possible so
|
* return false to tell caller to retry.
|
*/
|
if ((krcp->bkvhead[0] && !krwp->bkvhead_free[0]) ||
|
(krcp->bkvhead[1] && !krwp->bkvhead_free[1]) ||
|
(krcp->head && !krwp->head_free)) {
|
// Channel 1 corresponds to SLAB ptrs.
|
// Channel 2 corresponds to vmalloc ptrs.
|
for (j = 0; j < FREE_N_CHANNELS; j++) {
|
if (!krwp->bkvhead_free[j]) {
|
krwp->bkvhead_free[j] = krcp->bkvhead[j];
|
krcp->bkvhead[j] = NULL;
|
}
|
}
|
|
// Channel 3 corresponds to emergency path.
|
if (!krwp->head_free) {
|
krwp->head_free = krcp->head;
|
krcp->head = NULL;
|
}
|
|
WRITE_ONCE(krcp->count, 0);
|
|
/*
|
* One work is per one batch, so there are three
|
* "free channels", the batch can handle. It can
|
* be that the work is in the pending state when
|
* channels have been detached following by each
|
* other.
|
*/
|
queue_rcu_work(system_wq, &krwp->rcu_work);
|
}
|
|
// Repeat if any "free" corresponding channel is still busy.
|
if (krcp->bkvhead[0] || krcp->bkvhead[1] || krcp->head)
|
repeat = true;
|
}
|
|
return !repeat;
|
}
|
|
static inline void kfree_rcu_drain_unlock(struct kfree_rcu_cpu *krcp,
|
unsigned long flags)
|
{
|
// Attempt to start a new batch.
|
krcp->monitor_todo = false;
|
if (queue_kfree_rcu_work(krcp)) {
|
// Success! Our job is done here.
|
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
return;
|
}
|
|
// Previous RCU batch still in progress, try again later.
|
krcp->monitor_todo = true;
|
schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
|
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
}
|
|
/*
|
* This function is invoked after the KFREE_DRAIN_JIFFIES timeout.
|
* It invokes kfree_rcu_drain_unlock() to attempt to start another batch.
|
*/
|
static void kfree_rcu_monitor(struct work_struct *work)
|
{
|
unsigned long flags;
|
struct kfree_rcu_cpu *krcp = container_of(work, struct kfree_rcu_cpu,
|
monitor_work.work);
|
|
raw_spin_lock_irqsave(&krcp->lock, flags);
|
if (krcp->monitor_todo)
|
kfree_rcu_drain_unlock(krcp, flags);
|
else
|
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
}
|
|
static enum hrtimer_restart
|
schedule_page_work_fn(struct hrtimer *t)
|
{
|
struct kfree_rcu_cpu *krcp =
|
container_of(t, struct kfree_rcu_cpu, hrtimer);
|
|
queue_work(system_highpri_wq, &krcp->page_cache_work);
|
return HRTIMER_NORESTART;
|
}
|
|
static void fill_page_cache_func(struct work_struct *work)
|
{
|
struct kvfree_rcu_bulk_data *bnode;
|
struct kfree_rcu_cpu *krcp =
|
container_of(work, struct kfree_rcu_cpu,
|
page_cache_work);
|
unsigned long flags;
|
bool pushed;
|
int i;
|
|
for (i = 0; i < rcu_min_cached_objs; i++) {
|
bnode = (struct kvfree_rcu_bulk_data *)
|
__get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
|
|
if (!bnode)
|
break;
|
|
raw_spin_lock_irqsave(&krcp->lock, flags);
|
pushed = put_cached_bnode(krcp, bnode);
|
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
|
if (!pushed) {
|
free_page((unsigned long) bnode);
|
break;
|
}
|
}
|
|
atomic_set(&krcp->work_in_progress, 0);
|
}
|
|
static void
|
run_page_cache_worker(struct kfree_rcu_cpu *krcp)
|
{
|
if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
|
!atomic_xchg(&krcp->work_in_progress, 1)) {
|
hrtimer_init(&krcp->hrtimer, CLOCK_MONOTONIC,
|
HRTIMER_MODE_REL);
|
krcp->hrtimer.function = schedule_page_work_fn;
|
hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL);
|
}
|
}
|
|
static inline bool
|
kvfree_call_rcu_add_ptr_to_bulk(struct kfree_rcu_cpu *krcp, void *ptr)
|
{
|
struct kvfree_rcu_bulk_data *bnode;
|
int idx;
|
|
if (unlikely(!krcp->initialized))
|
return false;
|
|
lockdep_assert_held(&krcp->lock);
|
idx = !!is_vmalloc_addr(ptr);
|
|
/* Check if a new block is required. */
|
if (!krcp->bkvhead[idx] ||
|
krcp->bkvhead[idx]->nr_records == KVFREE_BULK_MAX_ENTR) {
|
bnode = get_cached_bnode(krcp);
|
/* Switch to emergency path. */
|
if (!bnode)
|
return false;
|
|
/* Initialize the new block. */
|
bnode->nr_records = 0;
|
bnode->next = krcp->bkvhead[idx];
|
|
/* Attach it to the head. */
|
krcp->bkvhead[idx] = bnode;
|
}
|
|
/* Finally insert. */
|
krcp->bkvhead[idx]->records
|
[krcp->bkvhead[idx]->nr_records++] = ptr;
|
|
return true;
|
}
|
|
/*
|
* Queue a request for lazy invocation of appropriate free routine after a
|
* grace period. Please note there are three paths are maintained, two are the
|
* main ones that use array of pointers interface and third one is emergency
|
* one, that is used only when the main path can not be maintained temporary,
|
* due to memory pressure.
|
*
|
* Each kvfree_call_rcu() request is added to a batch. The batch will be drained
|
* every KFREE_DRAIN_JIFFIES number of jiffies. All the objects in the batch will
|
* be free'd in workqueue context. This allows us to: batch requests together to
|
* reduce the number of grace periods during heavy kfree_rcu()/kvfree_rcu() load.
|
*/
|
void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
|
{
|
unsigned long flags;
|
struct kfree_rcu_cpu *krcp;
|
bool success;
|
void *ptr;
|
|
if (head) {
|
ptr = (void *) head - (unsigned long) func;
|
} else {
|
/*
|
* Please note there is a limitation for the head-less
|
* variant, that is why there is a clear rule for such
|
* objects: it can be used from might_sleep() context
|
* only. For other places please embed an rcu_head to
|
* your data.
|
*/
|
might_sleep();
|
ptr = (unsigned long *) func;
|
}
|
|
krcp = krc_this_cpu_lock(&flags);
|
|
// Queue the object but don't yet schedule the batch.
|
if (debug_rcu_head_queue(ptr)) {
|
// Probable double kfree_rcu(), just leak.
|
WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n",
|
__func__, head);
|
|
// Mark as success and leave.
|
success = true;
|
goto unlock_return;
|
}
|
|
success = kvfree_call_rcu_add_ptr_to_bulk(krcp, ptr);
|
if (!success) {
|
run_page_cache_worker(krcp);
|
|
if (head == NULL)
|
// Inline if kvfree_rcu(one_arg) call.
|
goto unlock_return;
|
|
head->func = func;
|
head->next = krcp->head;
|
krcp->head = head;
|
success = true;
|
}
|
|
WRITE_ONCE(krcp->count, krcp->count + 1);
|
|
// Set timer to drain after KFREE_DRAIN_JIFFIES.
|
if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
|
!krcp->monitor_todo) {
|
krcp->monitor_todo = true;
|
schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
|
}
|
|
unlock_return:
|
krc_this_cpu_unlock(krcp, flags);
|
|
/*
|
* Inline kvfree() after synchronize_rcu(). We can do
|
* it from might_sleep() context only, so the current
|
* CPU can pass the QS state.
|
*/
|
if (!success) {
|
debug_rcu_head_unqueue((struct rcu_head *) ptr);
|
synchronize_rcu();
|
kvfree(ptr);
|
}
|
}
|
EXPORT_SYMBOL_GPL(kvfree_call_rcu);
|
|
static unsigned long
|
kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
|
{
|
int cpu;
|
unsigned long count = 0;
|
|
/* Snapshot count of all CPUs */
|
for_each_possible_cpu(cpu) {
|
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
|
|
count += READ_ONCE(krcp->count);
|
}
|
|
return count;
|
}
|
|
static unsigned long
|
kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
|
{
|
int cpu, freed = 0;
|
unsigned long flags;
|
|
for_each_possible_cpu(cpu) {
|
int count;
|
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
|
|
count = krcp->count;
|
raw_spin_lock_irqsave(&krcp->lock, flags);
|
if (krcp->monitor_todo)
|
kfree_rcu_drain_unlock(krcp, flags);
|
else
|
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
|
sc->nr_to_scan -= count;
|
freed += count;
|
|
if (sc->nr_to_scan <= 0)
|
break;
|
}
|
|
return freed == 0 ? SHRINK_STOP : freed;
|
}
|
|
static struct shrinker kfree_rcu_shrinker = {
|
.count_objects = kfree_rcu_shrink_count,
|
.scan_objects = kfree_rcu_shrink_scan,
|
.batch = 0,
|
.seeks = DEFAULT_SEEKS,
|
};
|
|
void __init kfree_rcu_scheduler_running(void)
|
{
|
int cpu;
|
unsigned long flags;
|
|
for_each_possible_cpu(cpu) {
|
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
|
|
raw_spin_lock_irqsave(&krcp->lock, flags);
|
if (!krcp->head || krcp->monitor_todo) {
|
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
continue;
|
}
|
krcp->monitor_todo = true;
|
schedule_delayed_work_on(cpu, &krcp->monitor_work,
|
KFREE_DRAIN_JIFFIES);
|
raw_spin_unlock_irqrestore(&krcp->lock, flags);
|
}
|
}
|
|
/*
|
* During early boot, any blocking grace-period wait automatically
|
* implies a grace period. Later on, this is never the case for PREEMPTION.
|
*
|
* Howevr, because a context switch is a grace period for !PREEMPTION, any
|
* blocking grace-period wait automatically implies a grace period if
|
* there is only one CPU online at any point time during execution of
|
* either synchronize_rcu() or synchronize_rcu_expedited(). It is OK to
|
* occasionally incorrectly indicate that there are multiple CPUs online
|
* when there was in fact only one the whole time, as this just adds some
|
* overhead: RCU still operates correctly.
|
*/
|
static int rcu_blocking_is_gp(void)
|
{
|
int ret;
|
|
if (IS_ENABLED(CONFIG_PREEMPTION))
|
return rcu_scheduler_active == RCU_SCHEDULER_INACTIVE;
|
might_sleep(); /* Check for RCU read-side critical section. */
|
preempt_disable();
|
ret = num_online_cpus() <= 1;
|
preempt_enable();
|
return ret;
|
}
|
|
/**
|
* synchronize_rcu - wait until a grace period has elapsed.
|
*
|
* Control will return to the caller some time after a full grace
|
* period has elapsed, in other words after all currently executing RCU
|
* read-side critical sections have completed. Note, however, that
|
* upon return from synchronize_rcu(), the caller might well be executing
|
* concurrently with new RCU read-side critical sections that began while
|
* synchronize_rcu() was waiting. RCU read-side critical sections are
|
* delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested.
|
* In addition, regions of code across which interrupts, preemption, or
|
* softirqs have been disabled also serve as RCU read-side critical
|
* sections. This includes hardware interrupt handlers, softirq handlers,
|
* and NMI handlers.
|
*
|
* Note that this guarantee implies further memory-ordering guarantees.
|
* On systems with more than one CPU, when synchronize_rcu() returns,
|
* each CPU is guaranteed to have executed a full memory barrier since
|
* the end of its last RCU read-side critical section whose beginning
|
* preceded the call to synchronize_rcu(). In addition, each CPU having
|
* an RCU read-side critical section that extends beyond the return from
|
* synchronize_rcu() is guaranteed to have executed a full memory barrier
|
* after the beginning of synchronize_rcu() and before the beginning of
|
* that RCU read-side critical section. Note that these guarantees include
|
* CPUs that are offline, idle, or executing in user mode, as well as CPUs
|
* that are executing in the kernel.
|
*
|
* Furthermore, if CPU A invoked synchronize_rcu(), which returned
|
* to its caller on CPU B, then both CPU A and CPU B are guaranteed
|
* to have executed a full memory barrier during the execution of
|
* synchronize_rcu() -- even if CPU A and CPU B are the same CPU (but
|
* again only if the system has more than one CPU).
|
*/
|
void synchronize_rcu(void)
|
{
|
RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
|
lock_is_held(&rcu_lock_map) ||
|
lock_is_held(&rcu_sched_lock_map),
|
"Illegal synchronize_rcu() in RCU read-side critical section");
|
if (rcu_blocking_is_gp())
|
return;
|
if (rcu_gp_is_expedited())
|
synchronize_rcu_expedited();
|
else
|
wait_rcu_gp(call_rcu);
|
}
|
EXPORT_SYMBOL_GPL(synchronize_rcu);
|
|
/**
|
* get_state_synchronize_rcu - Snapshot current RCU state
|
*
|
* Returns a cookie that is used by a later call to cond_synchronize_rcu()
|
* to determine whether or not a full grace period has elapsed in the
|
* meantime.
|
*/
|
unsigned long get_state_synchronize_rcu(void)
|
{
|
/*
|
* Any prior manipulation of RCU-protected data must happen
|
* before the load from ->gp_seq.
|
*/
|
smp_mb(); /* ^^^ */
|
return rcu_seq_snap(&rcu_state.gp_seq);
|
}
|
EXPORT_SYMBOL_GPL(get_state_synchronize_rcu);
|
|
/**
|
* cond_synchronize_rcu - Conditionally wait for an RCU grace period
|
*
|
* @oldstate: return value from earlier call to get_state_synchronize_rcu()
|
*
|
* If a full RCU grace period has elapsed since the earlier call to
|
* get_state_synchronize_rcu(), just return. Otherwise, invoke
|
* synchronize_rcu() to wait for a full grace period.
|
*
|
* Yes, this function does not take counter wrap into account. But
|
* counter wrap is harmless. If the counter wraps, we have waited for
|
* more than 2 billion grace periods (and way more on a 64-bit system!),
|
* so waiting for one additional grace period should be just fine.
|
*/
|
void cond_synchronize_rcu(unsigned long oldstate)
|
{
|
if (!rcu_seq_done(&rcu_state.gp_seq, oldstate))
|
synchronize_rcu();
|
else
|
smp_mb(); /* Ensure GP ends before subsequent accesses. */
|
}
|
EXPORT_SYMBOL_GPL(cond_synchronize_rcu);
|
|
/*
|
* Check to see if there is any immediate RCU-related work to be done by
|
* the current CPU, returning 1 if so and zero otherwise. The checks are
|
* in order of increasing expense: checks that can be carried out against
|
* CPU-local state are performed first. However, we must check for CPU
|
* stalls first, else we might not get a chance.
|
*/
|
static int rcu_pending(int user)
|
{
|
bool gp_in_progress;
|
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
|
struct rcu_node *rnp = rdp->mynode;
|
|
lockdep_assert_irqs_disabled();
|
|
/* Check for CPU stalls, if enabled. */
|
check_cpu_stall(rdp);
|
|
/* Does this CPU need a deferred NOCB wakeup? */
|
if (rcu_nocb_need_deferred_wakeup(rdp))
|
return 1;
|
|
/* Is this a nohz_full CPU in userspace or idle? (Ignore RCU if so.) */
|
if ((user || rcu_is_cpu_rrupt_from_idle()) && rcu_nohz_full_cpu())
|
return 0;
|
|
/* Is the RCU core waiting for a quiescent state from this CPU? */
|
gp_in_progress = rcu_gp_in_progress();
|
if (rdp->core_needs_qs && !rdp->cpu_no_qs.b.norm && gp_in_progress)
|
return 1;
|
|
/* Does this CPU have callbacks ready to invoke? */
|
if (rcu_segcblist_ready_cbs(&rdp->cblist))
|
return 1;
|
|
/* Has RCU gone idle with this CPU needing another grace period? */
|
if (!gp_in_progress && rcu_segcblist_is_enabled(&rdp->cblist) &&
|
(!IS_ENABLED(CONFIG_RCU_NOCB_CPU) ||
|
!rcu_segcblist_is_offloaded(&rdp->cblist)) &&
|
!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
|
return 1;
|
|
/* Have RCU grace period completed or started? */
|
if (rcu_seq_current(&rnp->gp_seq) != rdp->gp_seq ||
|
unlikely(READ_ONCE(rdp->gpwrap))) /* outside lock */
|
return 1;
|
|
/* nothing to do */
|
return 0;
|
}
|
|
/*
|
* Helper function for rcu_barrier() tracing. If tracing is disabled,
|
* the compiler is expected to optimize this away.
|
*/
|
static void rcu_barrier_trace(const char *s, int cpu, unsigned long done)
|
{
|
trace_rcu_barrier(rcu_state.name, s, cpu,
|
atomic_read(&rcu_state.barrier_cpu_count), done);
|
}
|
|
/*
|
* RCU callback function for rcu_barrier(). If we are last, wake
|
* up the task executing rcu_barrier().
|
*
|
* Note that the value of rcu_state.barrier_sequence must be captured
|
* before the atomic_dec_and_test(). Otherwise, if this CPU is not last,
|
* other CPUs might count the value down to zero before this CPU gets
|
* around to invoking rcu_barrier_trace(), which might result in bogus
|
* data from the next instance of rcu_barrier().
|
*/
|
static void rcu_barrier_callback(struct rcu_head *rhp)
|
{
|
unsigned long __maybe_unused s = rcu_state.barrier_sequence;
|
|
if (atomic_dec_and_test(&rcu_state.barrier_cpu_count)) {
|
rcu_barrier_trace(TPS("LastCB"), -1, s);
|
complete(&rcu_state.barrier_completion);
|
} else {
|
rcu_barrier_trace(TPS("CB"), -1, s);
|
}
|
}
|
|
/*
|
* Called with preemption disabled, and from cross-cpu IRQ context.
|
*/
|
static void rcu_barrier_func(void *cpu_in)
|
{
|
uintptr_t cpu = (uintptr_t)cpu_in;
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
|
rcu_barrier_trace(TPS("IRQ"), -1, rcu_state.barrier_sequence);
|
rdp->barrier_head.func = rcu_barrier_callback;
|
debug_rcu_head_queue(&rdp->barrier_head);
|
rcu_nocb_lock(rdp);
|
WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, jiffies));
|
if (rcu_segcblist_entrain(&rdp->cblist, &rdp->barrier_head)) {
|
atomic_inc(&rcu_state.barrier_cpu_count);
|
} else {
|
debug_rcu_head_unqueue(&rdp->barrier_head);
|
rcu_barrier_trace(TPS("IRQNQ"), -1,
|
rcu_state.barrier_sequence);
|
}
|
rcu_nocb_unlock(rdp);
|
}
|
|
/**
|
* rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
|
*
|
* Note that this primitive does not necessarily wait for an RCU grace period
|
* to complete. For example, if there are no RCU callbacks queued anywhere
|
* in the system, then rcu_barrier() is within its rights to return
|
* immediately, without waiting for anything, much less an RCU grace period.
|
*/
|
void rcu_barrier(void)
|
{
|
uintptr_t cpu;
|
struct rcu_data *rdp;
|
unsigned long s = rcu_seq_snap(&rcu_state.barrier_sequence);
|
|
rcu_barrier_trace(TPS("Begin"), -1, s);
|
|
/* Take mutex to serialize concurrent rcu_barrier() requests. */
|
mutex_lock(&rcu_state.barrier_mutex);
|
|
/* Did someone else do our work for us? */
|
if (rcu_seq_done(&rcu_state.barrier_sequence, s)) {
|
rcu_barrier_trace(TPS("EarlyExit"), -1,
|
rcu_state.barrier_sequence);
|
smp_mb(); /* caller's subsequent code after above check. */
|
mutex_unlock(&rcu_state.barrier_mutex);
|
return;
|
}
|
|
/* Mark the start of the barrier operation. */
|
rcu_seq_start(&rcu_state.barrier_sequence);
|
rcu_barrier_trace(TPS("Inc1"), -1, rcu_state.barrier_sequence);
|
|
/*
|
* Initialize the count to two rather than to zero in order
|
* to avoid a too-soon return to zero in case of an immediate
|
* invocation of the just-enqueued callback (or preemption of
|
* this task). Exclude CPU-hotplug operations to ensure that no
|
* offline non-offloaded CPU has callbacks queued.
|
*/
|
init_completion(&rcu_state.barrier_completion);
|
atomic_set(&rcu_state.barrier_cpu_count, 2);
|
get_online_cpus();
|
|
/*
|
* Force each CPU with callbacks to register a new callback.
|
* When that callback is invoked, we will know that all of the
|
* corresponding CPU's preceding callbacks have been invoked.
|
*/
|
for_each_possible_cpu(cpu) {
|
rdp = per_cpu_ptr(&rcu_data, cpu);
|
if (cpu_is_offline(cpu) &&
|
!rcu_segcblist_is_offloaded(&rdp->cblist))
|
continue;
|
if (rcu_segcblist_n_cbs(&rdp->cblist) && cpu_online(cpu)) {
|
rcu_barrier_trace(TPS("OnlineQ"), cpu,
|
rcu_state.barrier_sequence);
|
smp_call_function_single(cpu, rcu_barrier_func, (void *)cpu, 1);
|
} else if (rcu_segcblist_n_cbs(&rdp->cblist) &&
|
cpu_is_offline(cpu)) {
|
rcu_barrier_trace(TPS("OfflineNoCBQ"), cpu,
|
rcu_state.barrier_sequence);
|
local_irq_disable();
|
rcu_barrier_func((void *)cpu);
|
local_irq_enable();
|
} else if (cpu_is_offline(cpu)) {
|
rcu_barrier_trace(TPS("OfflineNoCBNoQ"), cpu,
|
rcu_state.barrier_sequence);
|
} else {
|
rcu_barrier_trace(TPS("OnlineNQ"), cpu,
|
rcu_state.barrier_sequence);
|
}
|
}
|
put_online_cpus();
|
|
/*
|
* Now that we have an rcu_barrier_callback() callback on each
|
* CPU, and thus each counted, remove the initial count.
|
*/
|
if (atomic_sub_and_test(2, &rcu_state.barrier_cpu_count))
|
complete(&rcu_state.barrier_completion);
|
|
/* Wait for all rcu_barrier_callback() callbacks to be invoked. */
|
wait_for_completion(&rcu_state.barrier_completion);
|
|
/* Mark the end of the barrier operation. */
|
rcu_barrier_trace(TPS("Inc2"), -1, rcu_state.barrier_sequence);
|
rcu_seq_end(&rcu_state.barrier_sequence);
|
|
/* Other rcu_barrier() invocations can now safely proceed. */
|
mutex_unlock(&rcu_state.barrier_mutex);
|
}
|
EXPORT_SYMBOL_GPL(rcu_barrier);
|
|
/*
|
* Propagate ->qsinitmask bits up the rcu_node tree to account for the
|
* first CPU in a given leaf rcu_node structure coming online. The caller
|
* must hold the corresponding leaf rcu_node ->lock with interrrupts
|
* disabled.
|
*/
|
static void rcu_init_new_rnp(struct rcu_node *rnp_leaf)
|
{
|
long mask;
|
long oldmask;
|
struct rcu_node *rnp = rnp_leaf;
|
|
raw_lockdep_assert_held_rcu_node(rnp_leaf);
|
WARN_ON_ONCE(rnp->wait_blkd_tasks);
|
for (;;) {
|
mask = rnp->grpmask;
|
rnp = rnp->parent;
|
if (rnp == NULL)
|
return;
|
raw_spin_lock_rcu_node(rnp); /* Interrupts already disabled. */
|
oldmask = rnp->qsmaskinit;
|
rnp->qsmaskinit |= mask;
|
raw_spin_unlock_rcu_node(rnp); /* Interrupts remain disabled. */
|
if (oldmask)
|
return;
|
}
|
}
|
|
/*
|
* Do boot-time initialization of a CPU's per-CPU RCU data.
|
*/
|
static void __init
|
rcu_boot_init_percpu_data(int cpu)
|
{
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
|
/* Set up local state, ensuring consistent view of global state. */
|
rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu);
|
INIT_WORK(&rdp->strict_work, strict_work_handler);
|
WARN_ON_ONCE(rdp->dynticks_nesting != 1);
|
WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp)));
|
rdp->rcu_ofl_gp_seq = rcu_state.gp_seq;
|
rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED;
|
rdp->rcu_onl_gp_seq = rcu_state.gp_seq;
|
rdp->rcu_onl_gp_flags = RCU_GP_CLEANED;
|
rdp->cpu = cpu;
|
rcu_boot_init_nocb_percpu_data(rdp);
|
}
|
|
/*
|
* Invoked early in the CPU-online process, when pretty much all services
|
* are available. The incoming CPU is not present.
|
*
|
* Initializes a CPU's per-CPU RCU data. Note that only one online or
|
* offline event can be happening at a given time. Note also that we can
|
* accept some slop in the rsp->gp_seq access due to the fact that this
|
* CPU cannot possibly have any non-offloaded RCU callbacks in flight yet.
|
* And any offloaded callbacks are being numbered elsewhere.
|
*/
|
int rcutree_prepare_cpu(unsigned int cpu)
|
{
|
unsigned long flags;
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
struct rcu_node *rnp = rcu_get_root();
|
|
/* Set up local state, ensuring consistent view of global state. */
|
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
rdp->qlen_last_fqs_check = 0;
|
rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
|
rdp->blimit = blimit;
|
if (rcu_segcblist_empty(&rdp->cblist) && /* No early-boot CBs? */
|
!rcu_segcblist_is_offloaded(&rdp->cblist))
|
rcu_segcblist_init(&rdp->cblist); /* Re-enable callbacks. */
|
rdp->dynticks_nesting = 1; /* CPU not up, no tearing. */
|
rcu_dynticks_eqs_online();
|
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
|
|
/*
|
* Add CPU to leaf rcu_node pending-online bitmask. Any needed
|
* propagation up the rcu_node tree will happen at the beginning
|
* of the next grace period.
|
*/
|
rnp = rdp->mynode;
|
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
|
rdp->beenonline = true; /* We have now been online. */
|
rdp->gp_seq = READ_ONCE(rnp->gp_seq);
|
rdp->gp_seq_needed = rdp->gp_seq;
|
rdp->cpu_no_qs.b.norm = true;
|
rdp->core_needs_qs = false;
|
rdp->rcu_iw_pending = false;
|
rdp->rcu_iw_gp_seq = rdp->gp_seq - 1;
|
trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuonl"));
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
rcu_prepare_kthreads(cpu);
|
rcu_spawn_cpu_nocb_kthread(cpu);
|
|
return 0;
|
}
|
|
/*
|
* Update RCU priority boot kthread affinity for CPU-hotplug changes.
|
*/
|
static void rcutree_affinity_setting(unsigned int cpu, int outgoing)
|
{
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
|
rcu_boost_kthread_setaffinity(rdp->mynode, outgoing);
|
}
|
|
/*
|
* Near the end of the CPU-online process. Pretty much all services
|
* enabled, and the CPU is now very much alive.
|
*/
|
int rcutree_online_cpu(unsigned int cpu)
|
{
|
unsigned long flags;
|
struct rcu_data *rdp;
|
struct rcu_node *rnp;
|
|
rdp = per_cpu_ptr(&rcu_data, cpu);
|
rnp = rdp->mynode;
|
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
rnp->ffmask |= rdp->grpmask;
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE)
|
return 0; /* Too early in boot for scheduler work. */
|
sync_sched_exp_online_cleanup(cpu);
|
rcutree_affinity_setting(cpu, -1);
|
|
// Stop-machine done, so allow nohz_full to disable tick.
|
tick_dep_clear(TICK_DEP_BIT_RCU);
|
return 0;
|
}
|
|
/*
|
* Near the beginning of the process. The CPU is still very much alive
|
* with pretty much all services enabled.
|
*/
|
int rcutree_offline_cpu(unsigned int cpu)
|
{
|
unsigned long flags;
|
struct rcu_data *rdp;
|
struct rcu_node *rnp;
|
|
rdp = per_cpu_ptr(&rcu_data, cpu);
|
rnp = rdp->mynode;
|
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
rnp->ffmask &= ~rdp->grpmask;
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
|
rcutree_affinity_setting(cpu, cpu);
|
|
// nohz_full CPUs need the tick for stop-machine to work quickly
|
tick_dep_set(TICK_DEP_BIT_RCU);
|
return 0;
|
}
|
|
/*
|
* Mark the specified CPU as being online so that subsequent grace periods
|
* (both expedited and normal) will wait on it. Note that this means that
|
* incoming CPUs are not allowed to use RCU read-side critical sections
|
* until this function is called. Failing to observe this restriction
|
* will result in lockdep splats.
|
*
|
* Note that this function is special in that it is invoked directly
|
* from the incoming CPU rather than from the cpuhp_step mechanism.
|
* This is because this function must be invoked at a precise location.
|
*/
|
void rcu_cpu_starting(unsigned int cpu)
|
{
|
unsigned long flags;
|
unsigned long mask;
|
struct rcu_data *rdp;
|
struct rcu_node *rnp;
|
bool newcpu;
|
|
rdp = per_cpu_ptr(&rcu_data, cpu);
|
if (rdp->cpu_started)
|
return;
|
rdp->cpu_started = true;
|
|
rnp = rdp->mynode;
|
mask = rdp->grpmask;
|
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext | mask);
|
newcpu = !(rnp->expmaskinitnext & mask);
|
rnp->expmaskinitnext |= mask;
|
/* Allow lockless access for expedited grace periods. */
|
smp_store_release(&rcu_state.ncpus, rcu_state.ncpus + newcpu); /* ^^^ */
|
ASSERT_EXCLUSIVE_WRITER(rcu_state.ncpus);
|
rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */
|
rdp->rcu_onl_gp_seq = READ_ONCE(rcu_state.gp_seq);
|
rdp->rcu_onl_gp_flags = READ_ONCE(rcu_state.gp_flags);
|
if (rnp->qsmask & mask) { /* RCU waiting on incoming CPU? */
|
rcu_disable_urgency_upon_qs(rdp);
|
/* Report QS -after- changing ->qsmaskinitnext! */
|
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
|
} else {
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
}
|
smp_mb(); /* Ensure RCU read-side usage follows above initialization. */
|
}
|
|
/*
|
* The outgoing function has no further need of RCU, so remove it from
|
* the rcu_node tree's ->qsmaskinitnext bit masks.
|
*
|
* Note that this function is special in that it is invoked directly
|
* from the outgoing CPU rather than from the cpuhp_step mechanism.
|
* This is because this function must be invoked at a precise location.
|
*/
|
void rcu_report_dead(unsigned int cpu)
|
{
|
unsigned long flags;
|
unsigned long mask;
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
|
|
/* QS for any half-done expedited grace period. */
|
preempt_disable();
|
rcu_report_exp_rdp(this_cpu_ptr(&rcu_data));
|
preempt_enable();
|
rcu_preempt_deferred_qs(current);
|
|
/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
|
mask = rdp->grpmask;
|
raw_spin_lock(&rcu_state.ofl_lock);
|
raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */
|
rdp->rcu_ofl_gp_seq = READ_ONCE(rcu_state.gp_seq);
|
rdp->rcu_ofl_gp_flags = READ_ONCE(rcu_state.gp_flags);
|
if (rnp->qsmask & mask) { /* RCU waiting on outgoing CPU? */
|
/* Report quiescent state -before- changing ->qsmaskinitnext! */
|
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
|
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
}
|
WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext & ~mask);
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
raw_spin_unlock(&rcu_state.ofl_lock);
|
|
rdp->cpu_started = false;
|
}
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
/*
|
* The outgoing CPU has just passed through the dying-idle state, and we
|
* are being invoked from the CPU that was IPIed to continue the offline
|
* operation. Migrate the outgoing CPU's callbacks to the current CPU.
|
*/
|
void rcutree_migrate_callbacks(int cpu)
|
{
|
unsigned long flags;
|
struct rcu_data *my_rdp;
|
struct rcu_node *my_rnp;
|
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
|
bool needwake;
|
|
if (rcu_segcblist_is_offloaded(&rdp->cblist) ||
|
rcu_segcblist_empty(&rdp->cblist))
|
return; /* No callbacks to migrate. */
|
|
local_irq_save(flags);
|
my_rdp = this_cpu_ptr(&rcu_data);
|
my_rnp = my_rdp->mynode;
|
rcu_nocb_lock(my_rdp); /* irqs already disabled. */
|
WARN_ON_ONCE(!rcu_nocb_flush_bypass(my_rdp, NULL, jiffies));
|
raw_spin_lock_rcu_node(my_rnp); /* irqs already disabled. */
|
/* Leverage recent GPs and set GP for new callbacks. */
|
needwake = rcu_advance_cbs(my_rnp, rdp) ||
|
rcu_advance_cbs(my_rnp, my_rdp);
|
rcu_segcblist_merge(&my_rdp->cblist, &rdp->cblist);
|
needwake = needwake || rcu_advance_cbs(my_rnp, my_rdp);
|
rcu_segcblist_disable(&rdp->cblist);
|
WARN_ON_ONCE(rcu_segcblist_empty(&my_rdp->cblist) !=
|
!rcu_segcblist_n_cbs(&my_rdp->cblist));
|
if (rcu_segcblist_is_offloaded(&my_rdp->cblist)) {
|
raw_spin_unlock_rcu_node(my_rnp); /* irqs remain disabled. */
|
__call_rcu_nocb_wake(my_rdp, true, flags);
|
} else {
|
rcu_nocb_unlock(my_rdp); /* irqs remain disabled. */
|
raw_spin_unlock_irqrestore_rcu_node(my_rnp, flags);
|
}
|
if (needwake)
|
rcu_gp_kthread_wake();
|
lockdep_assert_irqs_enabled();
|
WARN_ONCE(rcu_segcblist_n_cbs(&rdp->cblist) != 0 ||
|
!rcu_segcblist_empty(&rdp->cblist),
|
"rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, 1stCB=%p\n",
|
cpu, rcu_segcblist_n_cbs(&rdp->cblist),
|
rcu_segcblist_first_cb(&rdp->cblist));
|
}
|
#endif
|
|
/*
|
* On non-huge systems, use expedited RCU grace periods to make suspend
|
* and hibernation run faster.
|
*/
|
static int rcu_pm_notify(struct notifier_block *self,
|
unsigned long action, void *hcpu)
|
{
|
switch (action) {
|
case PM_HIBERNATION_PREPARE:
|
case PM_SUSPEND_PREPARE:
|
rcu_expedite_gp();
|
break;
|
case PM_POST_HIBERNATION:
|
case PM_POST_SUSPEND:
|
rcu_unexpedite_gp();
|
break;
|
default:
|
break;
|
}
|
return NOTIFY_OK;
|
}
|
|
/*
|
* Spawn the kthreads that handle RCU's grace periods.
|
*/
|
static int __init rcu_spawn_gp_kthread(void)
|
{
|
unsigned long flags;
|
int kthread_prio_in = kthread_prio;
|
struct rcu_node *rnp;
|
struct sched_param sp;
|
struct task_struct *t;
|
|
/* Force priority into range. */
|
if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 2
|
&& IS_BUILTIN(CONFIG_RCU_TORTURE_TEST))
|
kthread_prio = 2;
|
else if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1)
|
kthread_prio = 1;
|
else if (kthread_prio < 0)
|
kthread_prio = 0;
|
else if (kthread_prio > 99)
|
kthread_prio = 99;
|
|
if (kthread_prio != kthread_prio_in)
|
pr_alert("rcu_spawn_gp_kthread(): Limited prio to %d from %d\n",
|
kthread_prio, kthread_prio_in);
|
|
rcu_scheduler_fully_active = 1;
|
t = kthread_create(rcu_gp_kthread, NULL, "%s", rcu_state.name);
|
if (WARN_ONCE(IS_ERR(t), "%s: Could not start grace-period kthread, OOM is now expected behavior\n", __func__))
|
return 0;
|
if (kthread_prio) {
|
sp.sched_priority = kthread_prio;
|
sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
|
}
|
rnp = rcu_get_root();
|
raw_spin_lock_irqsave_rcu_node(rnp, flags);
|
WRITE_ONCE(rcu_state.gp_activity, jiffies);
|
WRITE_ONCE(rcu_state.gp_req_activity, jiffies);
|
// Reset .gp_activity and .gp_req_activity before setting .gp_kthread.
|
smp_store_release(&rcu_state.gp_kthread, t); /* ^^^ */
|
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
|
wake_up_process(t);
|
rcu_spawn_nocb_kthreads();
|
rcu_spawn_boost_kthreads();
|
rcu_spawn_core_kthreads();
|
return 0;
|
}
|
early_initcall(rcu_spawn_gp_kthread);
|
|
/*
|
* This function is invoked towards the end of the scheduler's
|
* initialization process. Before this is called, the idle task might
|
* contain synchronous grace-period primitives (during which time, this idle
|
* task is booting the system, and such primitives are no-ops). After this
|
* function is called, any synchronous grace-period primitives are run as
|
* expedited, with the requesting task driving the grace period forward.
|
* A later core_initcall() rcu_set_runtime_mode() will switch to full
|
* runtime RCU functionality.
|
*/
|
void rcu_scheduler_starting(void)
|
{
|
WARN_ON(num_online_cpus() != 1);
|
WARN_ON(nr_context_switches() > 0);
|
rcu_test_sync_prims();
|
rcu_scheduler_active = RCU_SCHEDULER_INIT;
|
rcu_test_sync_prims();
|
}
|
|
/*
|
* Helper function for rcu_init() that initializes the rcu_state structure.
|
*/
|
static void __init rcu_init_one(void)
|
{
|
static const char * const buf[] = RCU_NODE_NAME_INIT;
|
static const char * const fqs[] = RCU_FQS_NAME_INIT;
|
static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
|
static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
|
|
int levelspread[RCU_NUM_LVLS]; /* kids/node in each level. */
|
int cpustride = 1;
|
int i;
|
int j;
|
struct rcu_node *rnp;
|
|
BUILD_BUG_ON(RCU_NUM_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
|
|
/* Silence gcc 4.8 false positive about array index out of range. */
|
if (rcu_num_lvls <= 0 || rcu_num_lvls > RCU_NUM_LVLS)
|
panic("rcu_init_one: rcu_num_lvls out of range");
|
|
/* Initialize the level-tracking arrays. */
|
|
for (i = 1; i < rcu_num_lvls; i++)
|
rcu_state.level[i] =
|
rcu_state.level[i - 1] + num_rcu_lvl[i - 1];
|
rcu_init_levelspread(levelspread, num_rcu_lvl);
|
|
/* Initialize the elements themselves, starting from the leaves. */
|
|
for (i = rcu_num_lvls - 1; i >= 0; i--) {
|
cpustride *= levelspread[i];
|
rnp = rcu_state.level[i];
|
for (j = 0; j < num_rcu_lvl[i]; j++, rnp++) {
|
raw_spin_lock_init(&ACCESS_PRIVATE(rnp, lock));
|
lockdep_set_class_and_name(&ACCESS_PRIVATE(rnp, lock),
|
&rcu_node_class[i], buf[i]);
|
raw_spin_lock_init(&rnp->fqslock);
|
lockdep_set_class_and_name(&rnp->fqslock,
|
&rcu_fqs_class[i], fqs[i]);
|
rnp->gp_seq = rcu_state.gp_seq;
|
rnp->gp_seq_needed = rcu_state.gp_seq;
|
rnp->completedqs = rcu_state.gp_seq;
|
rnp->qsmask = 0;
|
rnp->qsmaskinit = 0;
|
rnp->grplo = j * cpustride;
|
rnp->grphi = (j + 1) * cpustride - 1;
|
if (rnp->grphi >= nr_cpu_ids)
|
rnp->grphi = nr_cpu_ids - 1;
|
if (i == 0) {
|
rnp->grpnum = 0;
|
rnp->grpmask = 0;
|
rnp->parent = NULL;
|
} else {
|
rnp->grpnum = j % levelspread[i - 1];
|
rnp->grpmask = BIT(rnp->grpnum);
|
rnp->parent = rcu_state.level[i - 1] +
|
j / levelspread[i - 1];
|
}
|
rnp->level = i;
|
INIT_LIST_HEAD(&rnp->blkd_tasks);
|
rcu_init_one_nocb(rnp);
|
init_waitqueue_head(&rnp->exp_wq[0]);
|
init_waitqueue_head(&rnp->exp_wq[1]);
|
init_waitqueue_head(&rnp->exp_wq[2]);
|
init_waitqueue_head(&rnp->exp_wq[3]);
|
spin_lock_init(&rnp->exp_lock);
|
}
|
}
|
|
init_swait_queue_head(&rcu_state.gp_wq);
|
init_swait_queue_head(&rcu_state.expedited_wq);
|
rnp = rcu_first_leaf_node();
|
for_each_possible_cpu(i) {
|
while (i > rnp->grphi)
|
rnp++;
|
per_cpu_ptr(&rcu_data, i)->mynode = rnp;
|
rcu_boot_init_percpu_data(i);
|
}
|
}
|
|
/*
|
* Compute the rcu_node tree geometry from kernel parameters. This cannot
|
* replace the definitions in tree.h because those are needed to size
|
* the ->node array in the rcu_state structure.
|
*/
|
void rcu_init_geometry(void)
|
{
|
ulong d;
|
int i;
|
static unsigned long old_nr_cpu_ids;
|
int rcu_capacity[RCU_NUM_LVLS];
|
static bool initialized;
|
|
if (initialized) {
|
/*
|
* Warn if setup_nr_cpu_ids() had not yet been invoked,
|
* unless nr_cpus_ids == NR_CPUS, in which case who cares?
|
*/
|
WARN_ON_ONCE(old_nr_cpu_ids != nr_cpu_ids);
|
return;
|
}
|
|
old_nr_cpu_ids = nr_cpu_ids;
|
initialized = true;
|
|
/*
|
* Initialize any unspecified boot parameters.
|
* The default values of jiffies_till_first_fqs and
|
* jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS
|
* value, which is a function of HZ, then adding one for each
|
* RCU_JIFFIES_FQS_DIV CPUs that might be on the system.
|
*/
|
d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV;
|
if (jiffies_till_first_fqs == ULONG_MAX)
|
jiffies_till_first_fqs = d;
|
if (jiffies_till_next_fqs == ULONG_MAX)
|
jiffies_till_next_fqs = d;
|
adjust_jiffies_till_sched_qs();
|
|
/* If the compile-time values are accurate, just leave. */
|
if (rcu_fanout_leaf == RCU_FANOUT_LEAF &&
|
nr_cpu_ids == NR_CPUS)
|
return;
|
pr_info("Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%u\n",
|
rcu_fanout_leaf, nr_cpu_ids);
|
|
/*
|
* The boot-time rcu_fanout_leaf parameter must be at least two
|
* and cannot exceed the number of bits in the rcu_node masks.
|
* Complain and fall back to the compile-time values if this
|
* limit is exceeded.
|
*/
|
if (rcu_fanout_leaf < 2 ||
|
rcu_fanout_leaf > sizeof(unsigned long) * 8) {
|
rcu_fanout_leaf = RCU_FANOUT_LEAF;
|
WARN_ON(1);
|
return;
|
}
|
|
/*
|
* Compute number of nodes that can be handled an rcu_node tree
|
* with the given number of levels.
|
*/
|
rcu_capacity[0] = rcu_fanout_leaf;
|
for (i = 1; i < RCU_NUM_LVLS; i++)
|
rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT;
|
|
/*
|
* The tree must be able to accommodate the configured number of CPUs.
|
* If this limit is exceeded, fall back to the compile-time values.
|
*/
|
if (nr_cpu_ids > rcu_capacity[RCU_NUM_LVLS - 1]) {
|
rcu_fanout_leaf = RCU_FANOUT_LEAF;
|
WARN_ON(1);
|
return;
|
}
|
|
/* Calculate the number of levels in the tree. */
|
for (i = 0; nr_cpu_ids > rcu_capacity[i]; i++) {
|
}
|
rcu_num_lvls = i + 1;
|
|
/* Calculate the number of rcu_nodes at each level of the tree. */
|
for (i = 0; i < rcu_num_lvls; i++) {
|
int cap = rcu_capacity[(rcu_num_lvls - 1) - i];
|
num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap);
|
}
|
|
/* Calculate the total number of rcu_node structures. */
|
rcu_num_nodes = 0;
|
for (i = 0; i < rcu_num_lvls; i++)
|
rcu_num_nodes += num_rcu_lvl[i];
|
}
|
|
/*
|
* Dump out the structure of the rcu_node combining tree associated
|
* with the rcu_state structure.
|
*/
|
static void __init rcu_dump_rcu_node_tree(void)
|
{
|
int level = 0;
|
struct rcu_node *rnp;
|
|
pr_info("rcu_node tree layout dump\n");
|
pr_info(" ");
|
rcu_for_each_node_breadth_first(rnp) {
|
if (rnp->level != level) {
|
pr_cont("\n");
|
pr_info(" ");
|
level = rnp->level;
|
}
|
pr_cont("%d:%d ^%d ", rnp->grplo, rnp->grphi, rnp->grpnum);
|
}
|
pr_cont("\n");
|
}
|
|
struct workqueue_struct *rcu_gp_wq;
|
struct workqueue_struct *rcu_par_gp_wq;
|
|
static void __init kfree_rcu_batch_init(void)
|
{
|
int cpu;
|
int i;
|
|
for_each_possible_cpu(cpu) {
|
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
|
|
for (i = 0; i < KFREE_N_BATCHES; i++) {
|
INIT_RCU_WORK(&krcp->krw_arr[i].rcu_work, kfree_rcu_work);
|
krcp->krw_arr[i].krcp = krcp;
|
}
|
|
INIT_DELAYED_WORK(&krcp->monitor_work, kfree_rcu_monitor);
|
INIT_WORK(&krcp->page_cache_work, fill_page_cache_func);
|
krcp->initialized = true;
|
}
|
if (register_shrinker(&kfree_rcu_shrinker))
|
pr_err("Failed to register kfree_rcu() shrinker!\n");
|
}
|
|
void __init rcu_init(void)
|
{
|
int cpu;
|
|
rcu_early_boot_tests();
|
|
kfree_rcu_batch_init();
|
rcu_bootup_announce();
|
rcu_init_geometry();
|
rcu_init_one();
|
if (dump_tree)
|
rcu_dump_rcu_node_tree();
|
if (use_softirq)
|
open_softirq(RCU_SOFTIRQ, rcu_core_si);
|
|
/*
|
* We don't need protection against CPU-hotplug here because
|
* this is called early in boot, before either interrupts
|
* or the scheduler are operational.
|
*/
|
pm_notifier(rcu_pm_notify, 0);
|
for_each_online_cpu(cpu) {
|
rcutree_prepare_cpu(cpu);
|
rcu_cpu_starting(cpu);
|
rcutree_online_cpu(cpu);
|
}
|
|
/* Create workqueue for expedited GPs and for Tree SRCU. */
|
rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_MEM_RECLAIM, 0);
|
WARN_ON(!rcu_gp_wq);
|
rcu_par_gp_wq = alloc_workqueue("rcu_par_gp", WQ_MEM_RECLAIM, 0);
|
WARN_ON(!rcu_par_gp_wq);
|
srcu_init();
|
|
/* Fill in default value for rcutree.qovld boot parameter. */
|
/* -After- the rcu_node ->lock fields are initialized! */
|
if (qovld < 0)
|
qovld_calc = DEFAULT_RCU_QOVLD_MULT * qhimark;
|
else
|
qovld_calc = qovld;
|
}
|
|
#include "tree_stall.h"
|
#include "tree_exp.h"
|
#include "tree_plugin.h"
|
