// SPDX-License-Identifier: GPL-2.0+
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/*
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* Read-Copy Update mechanism for mutual exclusion
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*
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* Copyright IBM Corporation, 2001
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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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*
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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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* Papers:
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* http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
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* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
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*
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* For detailed explanation of Read-Copy Update mechanism see -
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* http://lse.sourceforge.net/locking/rcupdate.html
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*
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*/
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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/interrupt.h>
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#include <linux/sched/signal.h>
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#include <linux/sched/debug.h>
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#include <linux/atomic.h>
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#include <linux/bitops.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/export.h>
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#include <linux/hardirq.h>
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#include <linux/delay.h>
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#include <linux/moduleparam.h>
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#include <linux/kthread.h>
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#include <linux/tick.h>
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#include <linux/rcupdate_wait.h>
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#include <linux/sched/isolation.h>
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#include <linux/kprobes.h>
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#include <linux/slab.h>
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#include <linux/irq_work.h>
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#include <linux/rcupdate_trace.h>
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#define CREATE_TRACE_POINTS
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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 "rcupdate."
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#ifndef CONFIG_TINY_RCU
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module_param(rcu_expedited, int, 0);
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module_param(rcu_normal, int, 0);
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static int rcu_normal_after_boot = IS_ENABLED(CONFIG_PREEMPT_RT);
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#ifndef CONFIG_PREEMPT_RT
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module_param(rcu_normal_after_boot, int, 0);
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#endif
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#endif /* #ifndef CONFIG_TINY_RCU */
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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/**
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* rcu_read_lock_held_common() - might we be in RCU-sched read-side critical section?
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* @ret: Best guess answer if lockdep cannot be relied on
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*
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* Returns true if lockdep must be ignored, in which case ``*ret`` contains
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* the best guess described below. Otherwise returns false, in which
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* case ``*ret`` tells the caller nothing and the caller should instead
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* consult lockdep.
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*
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* If CONFIG_DEBUG_LOCK_ALLOC is selected, set ``*ret`` to nonzero iff in an
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* RCU-sched read-side critical section. In absence of
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* CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
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* critical section unless it can prove otherwise. Note that disabling
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* of preemption (including disabling irqs) counts as an RCU-sched
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* read-side critical section. This is useful for debug checks in functions
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* that required that they be called within an RCU-sched read-side
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* critical section.
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*
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* Check debug_lockdep_rcu_enabled() to prevent false positives during boot
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* and while lockdep is disabled.
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*
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* Note that if the CPU is in the idle loop from an RCU point of view (ie:
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* that we are in the section between rcu_idle_enter() and rcu_idle_exit())
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* then rcu_read_lock_held() sets ``*ret`` to false even if the CPU did an
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* rcu_read_lock(). The reason for this is that RCU ignores CPUs that are
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* in such a section, considering these as in extended quiescent state,
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* so such a CPU is effectively never in an RCU read-side critical section
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* regardless of what RCU primitives it invokes. This state of affairs is
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* required --- we need to keep an RCU-free window in idle where the CPU may
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* possibly enter into low power mode. This way we can notice an extended
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* quiescent state to other CPUs that started a grace period. Otherwise
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* we would delay any grace period as long as we run in the idle task.
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*
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* Similarly, we avoid claiming an RCU read lock held if the current
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* CPU is offline.
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*/
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static bool rcu_read_lock_held_common(bool *ret)
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{
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if (!debug_lockdep_rcu_enabled()) {
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*ret = true;
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return true;
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}
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if (!rcu_is_watching()) {
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*ret = false;
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return true;
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}
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if (!rcu_lockdep_current_cpu_online()) {
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*ret = false;
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return true;
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}
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return false;
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}
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int rcu_read_lock_sched_held(void)
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{
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bool ret;
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if (rcu_read_lock_held_common(&ret))
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return ret;
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return lock_is_held(&rcu_sched_lock_map) || !preemptible();
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}
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EXPORT_SYMBOL(rcu_read_lock_sched_held);
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#endif
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#ifndef CONFIG_TINY_RCU
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/*
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* Should expedited grace-period primitives always fall back to their
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* non-expedited counterparts? Intended for use within RCU. Note
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* that if the user specifies both rcu_expedited and rcu_normal, then
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* rcu_normal wins. (Except during the time period during boot from
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* when the first task is spawned until the rcu_set_runtime_mode()
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* core_initcall() is invoked, at which point everything is expedited.)
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*/
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bool rcu_gp_is_normal(void)
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{
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return READ_ONCE(rcu_normal) &&
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rcu_scheduler_active != RCU_SCHEDULER_INIT;
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}
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EXPORT_SYMBOL_GPL(rcu_gp_is_normal);
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static atomic_t rcu_expedited_nesting = ATOMIC_INIT(1);
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/*
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* Should normal grace-period primitives be expedited? Intended for
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* use within RCU. Note that this function takes the rcu_expedited
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* sysfs/boot variable and rcu_scheduler_active into account as well
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* as the rcu_expedite_gp() nesting. So looping on rcu_unexpedite_gp()
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* until rcu_gp_is_expedited() returns false is a -really- bad idea.
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*/
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bool rcu_gp_is_expedited(void)
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{
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return rcu_expedited || atomic_read(&rcu_expedited_nesting);
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}
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EXPORT_SYMBOL_GPL(rcu_gp_is_expedited);
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/**
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* rcu_expedite_gp - Expedite future RCU grace periods
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*
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* After a call to this function, future calls to synchronize_rcu() and
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* friends act as the corresponding synchronize_rcu_expedited() function
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* had instead been called.
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*/
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void rcu_expedite_gp(void)
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{
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atomic_inc(&rcu_expedited_nesting);
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}
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EXPORT_SYMBOL_GPL(rcu_expedite_gp);
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/**
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* rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation
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*
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* Undo a prior call to rcu_expedite_gp(). If all prior calls to
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* rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(),
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* and if the rcu_expedited sysfs/boot parameter is not set, then all
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* subsequent calls to synchronize_rcu() and friends will return to
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* their normal non-expedited behavior.
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*/
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void rcu_unexpedite_gp(void)
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{
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atomic_dec(&rcu_expedited_nesting);
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}
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EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
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static bool rcu_boot_ended __read_mostly;
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/*
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* Inform RCU of the end of the in-kernel boot sequence.
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*/
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void rcu_end_inkernel_boot(void)
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{
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rcu_unexpedite_gp();
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if (rcu_normal_after_boot)
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WRITE_ONCE(rcu_normal, 1);
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rcu_boot_ended = true;
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}
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/*
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* Let rcutorture know when it is OK to turn it up to eleven.
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*/
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bool rcu_inkernel_boot_has_ended(void)
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{
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return rcu_boot_ended;
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}
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EXPORT_SYMBOL_GPL(rcu_inkernel_boot_has_ended);
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#endif /* #ifndef CONFIG_TINY_RCU */
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/*
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* Test each non-SRCU synchronous grace-period wait API. This is
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* useful just after a change in mode for these primitives, and
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* during early boot.
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*/
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void rcu_test_sync_prims(void)
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{
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if (!IS_ENABLED(CONFIG_PROVE_RCU))
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return;
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synchronize_rcu();
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synchronize_rcu_expedited();
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}
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#if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU)
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/*
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* Switch to run-time mode once RCU has fully initialized.
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*/
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static int __init rcu_set_runtime_mode(void)
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{
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rcu_test_sync_prims();
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rcu_scheduler_active = RCU_SCHEDULER_RUNNING;
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kfree_rcu_scheduler_running();
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rcu_test_sync_prims();
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return 0;
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}
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core_initcall(rcu_set_runtime_mode);
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#endif /* #if !defined(CONFIG_TINY_RCU) || defined(CONFIG_SRCU) */
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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static struct lock_class_key rcu_lock_key;
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struct lockdep_map rcu_lock_map = {
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.name = "rcu_read_lock",
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.key = &rcu_lock_key,
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.wait_type_outer = LD_WAIT_FREE,
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.wait_type_inner = LD_WAIT_CONFIG, /* XXX PREEMPT_RCU ? */
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};
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EXPORT_SYMBOL_GPL(rcu_lock_map);
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static struct lock_class_key rcu_bh_lock_key;
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struct lockdep_map rcu_bh_lock_map = {
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.name = "rcu_read_lock_bh",
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.key = &rcu_bh_lock_key,
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.wait_type_outer = LD_WAIT_FREE,
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.wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_LOCK also makes BH preemptible */
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};
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EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
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static struct lock_class_key rcu_sched_lock_key;
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struct lockdep_map rcu_sched_lock_map = {
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.name = "rcu_read_lock_sched",
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.key = &rcu_sched_lock_key,
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.wait_type_outer = LD_WAIT_FREE,
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.wait_type_inner = LD_WAIT_SPIN,
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};
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EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
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// Tell lockdep when RCU callbacks are being invoked.
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static struct lock_class_key rcu_callback_key;
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struct lockdep_map rcu_callback_map =
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STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key);
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EXPORT_SYMBOL_GPL(rcu_callback_map);
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noinstr int notrace debug_lockdep_rcu_enabled(void)
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{
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return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && READ_ONCE(debug_locks) &&
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current->lockdep_recursion == 0;
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}
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EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
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/**
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* rcu_read_lock_held() - might we be in RCU read-side critical section?
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*
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* If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU
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* read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
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* this assumes we are in an RCU read-side critical section unless it can
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* prove otherwise. This is useful for debug checks in functions that
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* require that they be called within an RCU read-side critical section.
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*
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* Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
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* and while lockdep is disabled.
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*
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* Note that rcu_read_lock() and the matching rcu_read_unlock() must
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* occur in the same context, for example, it is illegal to invoke
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* rcu_read_unlock() in process context if the matching rcu_read_lock()
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* was invoked from within an irq handler.
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*
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* Note that rcu_read_lock() is disallowed if the CPU is either idle or
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* offline from an RCU perspective, so check for those as well.
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*/
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int rcu_read_lock_held(void)
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{
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bool ret;
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if (rcu_read_lock_held_common(&ret))
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return ret;
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return lock_is_held(&rcu_lock_map);
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}
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EXPORT_SYMBOL_GPL(rcu_read_lock_held);
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/**
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* rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
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*
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* Check for bottom half being disabled, which covers both the
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* CONFIG_PROVE_RCU and not cases. Note that if someone uses
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* rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
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* will show the situation. This is useful for debug checks in functions
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* that require that they be called within an RCU read-side critical
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* section.
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*
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* Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
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*
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* Note that rcu_read_lock_bh() is disallowed if the CPU is either idle or
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* offline from an RCU perspective, so check for those as well.
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*/
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int rcu_read_lock_bh_held(void)
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{
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bool ret;
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if (rcu_read_lock_held_common(&ret))
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return ret;
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return in_softirq() || irqs_disabled();
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}
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EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
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int rcu_read_lock_any_held(void)
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{
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bool ret;
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if (rcu_read_lock_held_common(&ret))
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return ret;
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if (lock_is_held(&rcu_lock_map) ||
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lock_is_held(&rcu_bh_lock_map) ||
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lock_is_held(&rcu_sched_lock_map))
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return 1;
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return !preemptible();
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}
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EXPORT_SYMBOL_GPL(rcu_read_lock_any_held);
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#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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/**
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* wakeme_after_rcu() - Callback function to awaken a task after grace period
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* @head: Pointer to rcu_head member within rcu_synchronize structure
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*
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* Awaken the corresponding task now that a grace period has elapsed.
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*/
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void wakeme_after_rcu(struct rcu_head *head)
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{
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struct rcu_synchronize *rcu;
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rcu = container_of(head, struct rcu_synchronize, head);
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complete(&rcu->completion);
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}
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EXPORT_SYMBOL_GPL(wakeme_after_rcu);
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void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
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struct rcu_synchronize *rs_array)
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{
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int i;
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int j;
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/* Initialize and register callbacks for each crcu_array element. */
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for (i = 0; i < n; i++) {
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if (checktiny &&
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(crcu_array[i] == call_rcu)) {
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might_sleep();
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continue;
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}
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for (j = 0; j < i; j++)
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if (crcu_array[j] == crcu_array[i])
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break;
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if (j == i) {
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init_rcu_head_on_stack(&rs_array[i].head);
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init_completion(&rs_array[i].completion);
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(crcu_array[i])(&rs_array[i].head, wakeme_after_rcu);
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}
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}
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/* Wait for all callbacks to be invoked. */
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for (i = 0; i < n; i++) {
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if (checktiny &&
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(crcu_array[i] == call_rcu))
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continue;
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for (j = 0; j < i; j++)
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if (crcu_array[j] == crcu_array[i])
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break;
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if (j == i) {
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wait_for_completion(&rs_array[i].completion);
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destroy_rcu_head_on_stack(&rs_array[i].head);
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}
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}
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}
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EXPORT_SYMBOL_GPL(__wait_rcu_gp);
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#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
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void init_rcu_head(struct rcu_head *head)
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{
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debug_object_init(head, &rcuhead_debug_descr);
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}
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EXPORT_SYMBOL_GPL(init_rcu_head);
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void destroy_rcu_head(struct rcu_head *head)
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{
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debug_object_free(head, &rcuhead_debug_descr);
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}
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EXPORT_SYMBOL_GPL(destroy_rcu_head);
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static bool rcuhead_is_static_object(void *addr)
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{
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return true;
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}
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/**
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* init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
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* @head: pointer to rcu_head structure to be initialized
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*
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* This function informs debugobjects of a new rcu_head structure that
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* has been allocated as an auto variable on the stack. This function
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* is not required for rcu_head structures that are statically defined or
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* that are dynamically allocated on the heap. This function has no
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* effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
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*/
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void init_rcu_head_on_stack(struct rcu_head *head)
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{
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debug_object_init_on_stack(head, &rcuhead_debug_descr);
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}
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EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
|
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/**
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* destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
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* @head: pointer to rcu_head structure to be initialized
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*
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* This function informs debugobjects that an on-stack rcu_head structure
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* is about to go out of scope. As with init_rcu_head_on_stack(), this
|
* function is not required for rcu_head structures that are statically
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* defined or that are dynamically allocated on the heap. Also as with
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* init_rcu_head_on_stack(), this function has no effect for
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* !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
|
*/
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void destroy_rcu_head_on_stack(struct rcu_head *head)
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{
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debug_object_free(head, &rcuhead_debug_descr);
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}
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EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
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const struct debug_obj_descr rcuhead_debug_descr = {
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.name = "rcu_head",
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.is_static_object = rcuhead_is_static_object,
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};
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EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
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#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
|
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#if defined(CONFIG_TREE_RCU) || defined(CONFIG_RCU_TRACE)
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void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp,
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unsigned long secs,
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unsigned long c_old, unsigned long c)
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{
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trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c);
|
}
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EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
|
#else
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#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
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do { } while (0)
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#endif
|
|
#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST)
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/* Get rcutorture access to sched_setaffinity(). */
|
long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
|
{
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int ret;
|
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ret = sched_setaffinity(pid, in_mask);
|
WARN_ONCE(ret, "%s: sched_setaffinity() returned %d\n", __func__, ret);
|
return ret;
|
}
|
EXPORT_SYMBOL_GPL(rcutorture_sched_setaffinity);
|
#endif
|
|
#ifdef CONFIG_RCU_STALL_COMMON
|
int rcu_cpu_stall_ftrace_dump __read_mostly;
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module_param(rcu_cpu_stall_ftrace_dump, int, 0644);
|
int rcu_cpu_stall_suppress __read_mostly; // !0 = suppress stall warnings.
|
EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress);
|
module_param(rcu_cpu_stall_suppress, int, 0644);
|
int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
|
module_param(rcu_cpu_stall_timeout, int, 0644);
|
#endif /* #ifdef CONFIG_RCU_STALL_COMMON */
|
|
// Suppress boot-time RCU CPU stall warnings and rcutorture writer stall
|
// warnings. Also used by rcutorture even if stall warnings are excluded.
|
int rcu_cpu_stall_suppress_at_boot __read_mostly; // !0 = suppress boot stalls.
|
EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress_at_boot);
|
module_param(rcu_cpu_stall_suppress_at_boot, int, 0444);
|
|
#ifdef CONFIG_PROVE_RCU
|
|
/*
|
* Early boot self test parameters.
|
*/
|
static bool rcu_self_test;
|
module_param(rcu_self_test, bool, 0444);
|
|
static int rcu_self_test_counter;
|
|
static void test_callback(struct rcu_head *r)
|
{
|
rcu_self_test_counter++;
|
pr_info("RCU test callback executed %d\n", rcu_self_test_counter);
|
}
|
|
DEFINE_STATIC_SRCU(early_srcu);
|
|
struct early_boot_kfree_rcu {
|
struct rcu_head rh;
|
};
|
|
static void early_boot_test_call_rcu(void)
|
{
|
static struct rcu_head head;
|
static struct rcu_head shead;
|
struct early_boot_kfree_rcu *rhp;
|
|
call_rcu(&head, test_callback);
|
if (IS_ENABLED(CONFIG_SRCU))
|
call_srcu(&early_srcu, &shead, test_callback);
|
rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
|
if (!WARN_ON_ONCE(!rhp))
|
kfree_rcu(rhp, rh);
|
}
|
|
void rcu_early_boot_tests(void)
|
{
|
pr_info("Running RCU self tests\n");
|
|
if (rcu_self_test)
|
early_boot_test_call_rcu();
|
rcu_test_sync_prims();
|
}
|
|
static int rcu_verify_early_boot_tests(void)
|
{
|
int ret = 0;
|
int early_boot_test_counter = 0;
|
|
if (rcu_self_test) {
|
early_boot_test_counter++;
|
rcu_barrier();
|
if (IS_ENABLED(CONFIG_SRCU)) {
|
early_boot_test_counter++;
|
srcu_barrier(&early_srcu);
|
}
|
}
|
if (rcu_self_test_counter != early_boot_test_counter) {
|
WARN_ON(1);
|
ret = -1;
|
}
|
|
return ret;
|
}
|
late_initcall(rcu_verify_early_boot_tests);
|
#else
|
void rcu_early_boot_tests(void) {}
|
#endif /* CONFIG_PROVE_RCU */
|
|
#include "tasks.h"
|
|
#ifndef CONFIG_TINY_RCU
|
|
/*
|
* Print any significant non-default boot-time settings.
|
*/
|
void __init rcupdate_announce_bootup_oddness(void)
|
{
|
if (rcu_normal)
|
pr_info("\tNo expedited grace period (rcu_normal).\n");
|
else if (rcu_normal_after_boot)
|
pr_info("\tNo expedited grace period (rcu_normal_after_boot).\n");
|
else if (rcu_expedited)
|
pr_info("\tAll grace periods are expedited (rcu_expedited).\n");
|
if (rcu_cpu_stall_suppress)
|
pr_info("\tRCU CPU stall warnings suppressed (rcu_cpu_stall_suppress).\n");
|
if (rcu_cpu_stall_timeout != CONFIG_RCU_CPU_STALL_TIMEOUT)
|
pr_info("\tRCU CPU stall warnings timeout set to %d (rcu_cpu_stall_timeout).\n", rcu_cpu_stall_timeout);
|
rcu_tasks_bootup_oddness();
|
}
|
|
#endif /* #ifndef CONFIG_TINY_RCU */
|
