/* 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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* Internal non-public definitions.
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*
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* Copyright IBM Corporation, 2008
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*
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* Author: Ingo Molnar <mingo@elte.hu>
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* Paul E. McKenney <paulmck@linux.ibm.com>
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*/
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#include <linux/cache.h>
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#include <linux/spinlock.h>
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#include <linux/rtmutex.h>
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#include <linux/threads.h>
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#include <linux/cpumask.h>
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#include <linux/seqlock.h>
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#include <linux/swait.h>
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#include <linux/rcu_node_tree.h>
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#include "rcu_segcblist.h"
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/* Communicate arguments to a workqueue handler. */
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struct rcu_exp_work {
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unsigned long rew_s;
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struct work_struct rew_work;
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};
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/* RCU's kthread states for tracing. */
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#define RCU_KTHREAD_STOPPED 0
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#define RCU_KTHREAD_RUNNING 1
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#define RCU_KTHREAD_WAITING 2
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#define RCU_KTHREAD_OFFCPU 3
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#define RCU_KTHREAD_YIELDING 4
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#define RCU_KTHREAD_MAX 4
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/*
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* Definition for node within the RCU grace-period-detection hierarchy.
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*/
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struct rcu_node {
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raw_spinlock_t __private lock; /* Root rcu_node's lock protects */
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/* some rcu_state fields as well as */
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/* following. */
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unsigned long gp_seq; /* Track rsp->gp_seq. */
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unsigned long gp_seq_needed; /* Track furthest future GP request. */
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unsigned long completedqs; /* All QSes done for this node. */
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unsigned long qsmask; /* CPUs or groups that need to switch in */
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/* order for current grace period to proceed.*/
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/* In leaf rcu_node, each bit corresponds to */
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/* an rcu_data structure, otherwise, each */
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/* bit corresponds to a child rcu_node */
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/* structure. */
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unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */
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unsigned long qsmaskinit;
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/* Per-GP initial value for qsmask. */
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/* Initialized from ->qsmaskinitnext at the */
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/* beginning of each grace period. */
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unsigned long qsmaskinitnext;
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/* Online CPUs for next grace period. */
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unsigned long expmask; /* CPUs or groups that need to check in */
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/* to allow the current expedited GP */
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/* to complete. */
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unsigned long expmaskinit;
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/* Per-GP initial values for expmask. */
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/* Initialized from ->expmaskinitnext at the */
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/* beginning of each expedited GP. */
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unsigned long expmaskinitnext;
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/* Online CPUs for next expedited GP. */
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/* Any CPU that has ever been online will */
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/* have its bit set. */
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unsigned long cbovldmask;
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/* CPUs experiencing callback overload. */
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unsigned long ffmask; /* Fully functional CPUs. */
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unsigned long grpmask; /* Mask to apply to parent qsmask. */
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/* Only one bit will be set in this mask. */
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int grplo; /* lowest-numbered CPU here. */
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int grphi; /* highest-numbered CPU here. */
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u8 grpnum; /* group number for next level up. */
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u8 level; /* root is at level 0. */
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bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
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/* exit RCU read-side critical sections */
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/* before propagating offline up the */
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/* rcu_node tree? */
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struct rcu_node *parent;
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struct list_head blkd_tasks;
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/* Tasks blocked in RCU read-side critical */
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/* section. Tasks are placed at the head */
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/* of this list and age towards the tail. */
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struct list_head *gp_tasks;
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/* Pointer to the first task blocking the */
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/* current grace period, or NULL if there */
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/* is no such task. */
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struct list_head *exp_tasks;
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/* Pointer to the first task blocking the */
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/* current expedited grace period, or NULL */
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/* if there is no such task. If there */
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/* is no current expedited grace period, */
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/* then there can cannot be any such task. */
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struct list_head *boost_tasks;
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/* Pointer to first task that needs to be */
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/* priority boosted, or NULL if no priority */
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/* boosting is needed for this rcu_node */
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/* structure. If there are no tasks */
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/* queued on this rcu_node structure that */
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/* are blocking the current grace period, */
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/* there can be no such task. */
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struct rt_mutex boost_mtx;
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/* Used only for the priority-boosting */
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/* side effect, not as a lock. */
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unsigned long boost_time;
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/* When to start boosting (jiffies). */
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struct task_struct *boost_kthread_task;
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/* kthread that takes care of priority */
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/* boosting for this rcu_node structure. */
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unsigned int boost_kthread_status;
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/* State of boost_kthread_task for tracing. */
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#ifdef CONFIG_RCU_NOCB_CPU
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struct swait_queue_head nocb_gp_wq[2];
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/* Place for rcu_nocb_kthread() to wait GP. */
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#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
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raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
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spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
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unsigned long exp_seq_rq;
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wait_queue_head_t exp_wq[4];
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struct rcu_exp_work rew;
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bool exp_need_flush; /* Need to flush workitem? */
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} ____cacheline_internodealigned_in_smp;
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/*
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* Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
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* are indexed relative to this interval rather than the global CPU ID space.
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* This generates the bit for a CPU in node-local masks.
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*/
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#define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo))
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/*
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* Union to allow "aggregate OR" operation on the need for a quiescent
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* state by the normal and expedited grace periods.
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*/
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union rcu_noqs {
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struct {
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u8 norm;
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u8 exp;
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} b; /* Bits. */
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u16 s; /* Set of bits, aggregate OR here. */
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};
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/* Per-CPU data for read-copy update. */
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struct rcu_data {
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/* 1) quiescent-state and grace-period handling : */
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unsigned long gp_seq; /* Track rsp->gp_seq counter. */
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unsigned long gp_seq_needed; /* Track furthest future GP request. */
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union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */
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bool core_needs_qs; /* Core waits for quiesc state. */
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bool beenonline; /* CPU online at least once. */
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bool gpwrap; /* Possible ->gp_seq wrap. */
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bool exp_deferred_qs; /* This CPU awaiting a deferred QS? */
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bool cpu_started; /* RCU watching this onlining CPU. */
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struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
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unsigned long grpmask; /* Mask to apply to leaf qsmask. */
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unsigned long ticks_this_gp; /* The number of scheduling-clock */
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/* ticks this CPU has handled */
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/* during and after the last grace */
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/* period it is aware of. */
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struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */
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bool defer_qs_iw_pending; /* Scheduler attention pending? */
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struct work_struct strict_work; /* Schedule readers for strict GPs. */
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/* 2) batch handling */
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struct rcu_segcblist cblist; /* Segmented callback list, with */
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/* different callbacks waiting for */
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/* different grace periods. */
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long qlen_last_fqs_check;
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/* qlen at last check for QS forcing */
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unsigned long n_cbs_invoked; /* # callbacks invoked since boot. */
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unsigned long n_force_qs_snap;
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/* did other CPU force QS recently? */
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long blimit; /* Upper limit on a processed batch */
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/* 3) dynticks interface. */
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int dynticks_snap; /* Per-GP tracking for dynticks. */
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long dynticks_nesting; /* Track process nesting level. */
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long dynticks_nmi_nesting; /* Track irq/NMI nesting level. */
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atomic_t dynticks; /* Even value for idle, else odd. */
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bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */
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bool rcu_urgent_qs; /* GP old need light quiescent state. */
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bool rcu_forced_tick; /* Forced tick to provide QS. */
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bool rcu_forced_tick_exp; /* ... provide QS to expedited GP. */
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#ifdef CONFIG_RCU_FAST_NO_HZ
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unsigned long last_accelerate; /* Last jiffy CBs were accelerated. */
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unsigned long last_advance_all; /* Last jiffy CBs were all advanced. */
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int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
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#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
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/* 4) rcu_barrier(), OOM callbacks, and expediting. */
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struct rcu_head barrier_head;
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int exp_dynticks_snap; /* Double-check need for IPI. */
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/* 5) Callback offloading. */
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#ifdef CONFIG_RCU_NOCB_CPU
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struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */
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struct task_struct *nocb_gp_kthread;
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raw_spinlock_t nocb_lock; /* Guard following pair of fields. */
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atomic_t nocb_lock_contended; /* Contention experienced. */
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int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
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struct timer_list nocb_timer; /* Enforce finite deferral. */
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unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */
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/* The following fields are used by call_rcu, hence own cacheline. */
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raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp;
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struct rcu_cblist nocb_bypass; /* Lock-contention-bypass CB list. */
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unsigned long nocb_bypass_first; /* Time (jiffies) of first enqueue. */
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unsigned long nocb_nobypass_last; /* Last ->cblist enqueue (jiffies). */
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int nocb_nobypass_count; /* # ->cblist enqueues at ^^^ time. */
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/* The following fields are used by GP kthread, hence own cacheline. */
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raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp;
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struct timer_list nocb_bypass_timer; /* Force nocb_bypass flush. */
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u8 nocb_gp_sleep; /* Is the nocb GP thread asleep? */
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u8 nocb_gp_bypass; /* Found a bypass on last scan? */
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u8 nocb_gp_gp; /* GP to wait for on last scan? */
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unsigned long nocb_gp_seq; /* If so, ->gp_seq to wait for. */
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unsigned long nocb_gp_loops; /* # passes through wait code. */
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struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */
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bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */
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struct task_struct *nocb_cb_kthread;
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struct rcu_data *nocb_next_cb_rdp;
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/* Next rcu_data in wakeup chain. */
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/* The following fields are used by CB kthread, hence new cacheline. */
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struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp;
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/* GP rdp takes GP-end wakeups. */
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#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
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/* 6) RCU priority boosting. */
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struct task_struct *rcu_cpu_kthread_task;
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/* rcuc per-CPU kthread or NULL. */
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unsigned int rcu_cpu_kthread_status;
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char rcu_cpu_has_work;
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/* 7) Diagnostic data, including RCU CPU stall warnings. */
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unsigned int softirq_snap; /* Snapshot of softirq activity. */
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/* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
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struct irq_work rcu_iw; /* Check for non-irq activity. */
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bool rcu_iw_pending; /* Is ->rcu_iw pending? */
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unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */
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unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */
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short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */
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unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */
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short rcu_onl_gp_flags; /* ->gp_flags at last online. */
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unsigned long last_fqs_resched; /* Time of last rcu_resched(). */
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int cpu;
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};
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/* Values for nocb_defer_wakeup field in struct rcu_data. */
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#define RCU_NOCB_WAKE_NOT 0
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#define RCU_NOCB_WAKE 1
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#define RCU_NOCB_WAKE_FORCE 2
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#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
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/* For jiffies_till_first_fqs and */
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/* and jiffies_till_next_fqs. */
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#define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */
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/* delay between bouts of */
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/* quiescent-state forcing. */
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#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */
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/* at least one scheduling clock */
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/* irq before ratting on them. */
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#define rcu_wait(cond) \
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do { \
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for (;;) { \
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set_current_state(TASK_INTERRUPTIBLE); \
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if (cond) \
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break; \
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schedule(); \
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} \
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__set_current_state(TASK_RUNNING); \
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} while (0)
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/*
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* RCU global state, including node hierarchy. This hierarchy is
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* represented in "heap" form in a dense array. The root (first level)
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* of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
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* level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
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* and the third level in ->node[m+1] and following (->node[m+1] referenced
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* by ->level[2]). The number of levels is determined by the number of
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* CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy"
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* consisting of a single rcu_node.
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*/
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struct rcu_state {
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struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
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struct rcu_node *level[RCU_NUM_LVLS + 1];
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/* Hierarchy levels (+1 to */
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/* shut bogus gcc warning) */
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int ncpus; /* # CPUs seen so far. */
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/* The following fields are guarded by the root rcu_node's lock. */
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u8 boost ____cacheline_internodealigned_in_smp;
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/* Subject to priority boost. */
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unsigned long gp_seq; /* Grace-period sequence #. */
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unsigned long gp_max; /* Maximum GP duration in */
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/* jiffies. */
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struct task_struct *gp_kthread; /* Task for grace periods. */
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struct swait_queue_head gp_wq; /* Where GP task waits. */
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short gp_flags; /* Commands for GP task. */
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short gp_state; /* GP kthread sleep state. */
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unsigned long gp_wake_time; /* Last GP kthread wake. */
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unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */
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/* End of fields guarded by root rcu_node's lock. */
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struct mutex barrier_mutex; /* Guards barrier fields. */
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atomic_t barrier_cpu_count; /* # CPUs waiting on. */
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struct completion barrier_completion; /* Wake at barrier end. */
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unsigned long barrier_sequence; /* ++ at start and end of */
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/* rcu_barrier(). */
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/* End of fields guarded by barrier_mutex. */
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struct mutex exp_mutex; /* Serialize expedited GP. */
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struct mutex exp_wake_mutex; /* Serialize wakeup. */
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unsigned long expedited_sequence; /* Take a ticket. */
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atomic_t expedited_need_qs; /* # CPUs left to check in. */
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struct swait_queue_head expedited_wq; /* Wait for check-ins. */
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int ncpus_snap; /* # CPUs seen last time. */
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u8 cbovld; /* Callback overload now? */
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u8 cbovldnext; /* ^ ^ next time? */
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unsigned long jiffies_force_qs; /* Time at which to invoke */
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/* force_quiescent_state(). */
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unsigned long jiffies_kick_kthreads; /* Time at which to kick */
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/* kthreads, if configured. */
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unsigned long n_force_qs; /* Number of calls to */
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/* force_quiescent_state(). */
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unsigned long gp_start; /* Time at which GP started, */
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/* but in jiffies. */
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unsigned long gp_end; /* Time last GP ended, again */
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/* in jiffies. */
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unsigned long gp_activity; /* Time of last GP kthread */
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/* activity in jiffies. */
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unsigned long gp_req_activity; /* Time of last GP request */
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/* in jiffies. */
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unsigned long jiffies_stall; /* Time at which to check */
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/* for CPU stalls. */
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unsigned long jiffies_resched; /* Time at which to resched */
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/* a reluctant CPU. */
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unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */
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/* GP start. */
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const char *name; /* Name of structure. */
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char abbr; /* Abbreviated name. */
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raw_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
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/* Synchronize offline with */
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/* GP pre-initialization. */
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};
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/* Values for rcu_state structure's gp_flags field. */
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#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
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#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
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#define RCU_GP_FLAG_OVLD 0x4 /* Experiencing callback overload. */
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/* Values for rcu_state structure's gp_state field. */
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#define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */
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#define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */
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#define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */
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#define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */
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#define RCU_GP_INIT 4 /* Grace-period initialization. */
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#define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */
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#define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */
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#define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */
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#define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */
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/*
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* In order to export the rcu_state name to the tracing tools, it
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* needs to be added in the __tracepoint_string section.
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* This requires defining a separate variable tp_<sname>_varname
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* that points to the string being used, and this will allow
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* the tracing userspace tools to be able to decipher the string
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* address to the matching string.
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*/
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#ifdef CONFIG_PREEMPT_RCU
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#define RCU_ABBR 'p'
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#define RCU_NAME_RAW "rcu_preempt"
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#else /* #ifdef CONFIG_PREEMPT_RCU */
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#define RCU_ABBR 's'
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#define RCU_NAME_RAW "rcu_sched"
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#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
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#ifndef CONFIG_TRACING
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#define RCU_NAME RCU_NAME_RAW
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#else /* #ifdef CONFIG_TRACING */
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static char rcu_name[] = RCU_NAME_RAW;
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static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;
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#define RCU_NAME rcu_name
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#endif /* #else #ifdef CONFIG_TRACING */
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/* Forward declarations for tree_plugin.h */
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static void rcu_bootup_announce(void);
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static void rcu_qs(void);
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static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
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#ifdef CONFIG_HOTPLUG_CPU
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static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
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#endif /* #ifdef CONFIG_HOTPLUG_CPU */
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static int rcu_print_task_exp_stall(struct rcu_node *rnp);
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static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
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static void rcu_flavor_sched_clock_irq(int user);
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static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
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static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
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static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
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static bool rcu_is_callbacks_kthread(void);
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static void rcu_cpu_kthread_setup(unsigned int cpu);
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static void __init rcu_spawn_boost_kthreads(void);
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static void rcu_prepare_kthreads(int cpu);
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static void rcu_cleanup_after_idle(void);
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static void rcu_prepare_for_idle(void);
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static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
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static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
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static void rcu_preempt_deferred_qs(struct task_struct *t);
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static void zero_cpu_stall_ticks(struct rcu_data *rdp);
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static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
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static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
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static void rcu_init_one_nocb(struct rcu_node *rnp);
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static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
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unsigned long j);
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static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
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bool *was_alldone, unsigned long flags);
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static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
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unsigned long flags);
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static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
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static void do_nocb_deferred_wakeup(struct rcu_data *rdp);
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static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
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static void rcu_spawn_cpu_nocb_kthread(int cpu);
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static void __init rcu_spawn_nocb_kthreads(void);
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static void show_rcu_nocb_state(struct rcu_data *rdp);
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static void rcu_nocb_lock(struct rcu_data *rdp);
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static void rcu_nocb_unlock(struct rcu_data *rdp);
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static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
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unsigned long flags);
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static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp);
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#ifdef CONFIG_RCU_NOCB_CPU
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static void __init rcu_organize_nocb_kthreads(void);
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#define rcu_nocb_lock_irqsave(rdp, flags) \
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do { \
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if (!rcu_segcblist_is_offloaded(&(rdp)->cblist)) \
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local_irq_save(flags); \
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else \
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raw_spin_lock_irqsave(&(rdp)->nocb_lock, (flags)); \
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} while (0)
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#else /* #ifdef CONFIG_RCU_NOCB_CPU */
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#define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags)
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#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
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static void rcu_bind_gp_kthread(void);
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static bool rcu_nohz_full_cpu(void);
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static void rcu_dynticks_task_enter(void);
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static void rcu_dynticks_task_exit(void);
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static void rcu_dynticks_task_trace_enter(void);
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static void rcu_dynticks_task_trace_exit(void);
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/* Forward declarations for tree_stall.h */
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static void record_gp_stall_check_time(void);
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static void rcu_iw_handler(struct irq_work *iwp);
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static void check_cpu_stall(struct rcu_data *rdp);
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static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
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const unsigned long gpssdelay);
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