364 lines
10 KiB
C
364 lines
10 KiB
C
/*
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* Read-Copy Update mechanism for mutual exclusion
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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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@us.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.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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#define CREATE_TRACE_POINTS
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#include <trace/events/rcu.h>
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#include "rcu.h"
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#ifdef CONFIG_PREEMPT_RCU
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/*
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* Check for a task exiting while in a preemptible-RCU read-side
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* critical section, clean up if so. No need to issue warnings,
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* as debug_check_no_locks_held() already does this if lockdep
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* is enabled.
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*/
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void exit_rcu(void)
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{
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struct task_struct *t = current;
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if (likely(list_empty(¤t->rcu_node_entry)))
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return;
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t->rcu_read_lock_nesting = 1;
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barrier();
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t->rcu_read_unlock_special = RCU_READ_UNLOCK_BLOCKED;
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__rcu_read_unlock();
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}
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#else /* #ifdef CONFIG_PREEMPT_RCU */
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void exit_rcu(void)
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{
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}
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#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
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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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STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
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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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STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
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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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STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
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EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
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#endif
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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int debug_lockdep_rcu_enabled(void)
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{
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return rcu_scheduler_active && 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_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() 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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if (!debug_lockdep_rcu_enabled())
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return 1;
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if (rcu_is_cpu_idle())
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return 0;
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if (!rcu_lockdep_current_cpu_online())
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return 0;
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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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#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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struct rcu_synchronize {
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struct rcu_head head;
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struct completion completion;
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};
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/*
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* Awaken the corresponding synchronize_rcu() instance now that a
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* grace period has elapsed.
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*/
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static 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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void wait_rcu_gp(call_rcu_func_t crf)
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{
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struct rcu_synchronize rcu;
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init_rcu_head_on_stack(&rcu.head);
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init_completion(&rcu.completion);
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/* Will wake me after RCU finished. */
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crf(&rcu.head, wakeme_after_rcu);
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/* Wait for it. */
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wait_for_completion(&rcu.completion);
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destroy_rcu_head_on_stack(&rcu.head);
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}
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EXPORT_SYMBOL_GPL(wait_rcu_gp);
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#ifdef CONFIG_PROVE_RCU
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/*
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* wrapper function to avoid #include problems.
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*/
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int rcu_my_thread_group_empty(void)
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{
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return thread_group_empty(current);
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}
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EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty);
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#endif /* #ifdef CONFIG_PROVE_RCU */
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#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
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static inline void debug_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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static inline void debug_rcu_head_free(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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/*
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* fixup_init is called when:
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* - an active object is initialized
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*/
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static int rcuhead_fixup_init(void *addr, enum debug_obj_state state)
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{
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struct rcu_head *head = addr;
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switch (state) {
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case ODEBUG_STATE_ACTIVE:
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/*
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* Ensure that queued callbacks are all executed.
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* If we detect that we are nested in a RCU read-side critical
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* section, we should simply fail, otherwise we would deadlock.
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* In !PREEMPT configurations, there is no way to tell if we are
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* in a RCU read-side critical section or not, so we never
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* attempt any fixup and just print a warning.
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*/
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#ifndef CONFIG_PREEMPT
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WARN_ON_ONCE(1);
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return 0;
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#endif
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if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
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irqs_disabled()) {
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WARN_ON_ONCE(1);
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return 0;
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}
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rcu_barrier();
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rcu_barrier_sched();
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rcu_barrier_bh();
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debug_object_init(head, &rcuhead_debug_descr);
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return 1;
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default:
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return 0;
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}
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}
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/*
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* fixup_activate is called when:
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* - an active object is activated
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* - an unknown object is activated (might be a statically initialized object)
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* Activation is performed internally by call_rcu().
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*/
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static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state)
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{
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struct rcu_head *head = addr;
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switch (state) {
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case ODEBUG_STATE_NOTAVAILABLE:
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/*
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* This is not really a fixup. We just make sure that it is
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* tracked in the object tracker.
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*/
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debug_object_init(head, &rcuhead_debug_descr);
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debug_object_activate(head, &rcuhead_debug_descr);
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return 0;
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case ODEBUG_STATE_ACTIVE:
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/*
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* Ensure that queued callbacks are all executed.
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* If we detect that we are nested in a RCU read-side critical
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* section, we should simply fail, otherwise we would deadlock.
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* In !PREEMPT configurations, there is no way to tell if we are
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* in a RCU read-side critical section or not, so we never
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* attempt any fixup and just print a warning.
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*/
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#ifndef CONFIG_PREEMPT
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WARN_ON_ONCE(1);
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return 0;
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#endif
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if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
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irqs_disabled()) {
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WARN_ON_ONCE(1);
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return 0;
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}
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rcu_barrier();
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rcu_barrier_sched();
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rcu_barrier_bh();
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debug_object_activate(head, &rcuhead_debug_descr);
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return 1;
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default:
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return 0;
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}
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}
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/*
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* fixup_free is called when:
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* - an active object is freed
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*/
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static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
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{
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struct rcu_head *head = addr;
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switch (state) {
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case ODEBUG_STATE_ACTIVE:
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/*
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* Ensure that queued callbacks are all executed.
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* If we detect that we are nested in a RCU read-side critical
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* section, we should simply fail, otherwise we would deadlock.
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* In !PREEMPT configurations, there is no way to tell if we are
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* in a RCU read-side critical section or not, so we never
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* attempt any fixup and just print a warning.
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*/
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#ifndef CONFIG_PREEMPT
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WARN_ON_ONCE(1);
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return 0;
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#endif
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if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
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irqs_disabled()) {
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WARN_ON_ONCE(1);
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return 0;
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}
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rcu_barrier();
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rcu_barrier_sched();
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rcu_barrier_bh();
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debug_object_free(head, &rcuhead_debug_descr);
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return 1;
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default:
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return 0;
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}
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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
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* 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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*/
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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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struct debug_obj_descr rcuhead_debug_descr = {
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.name = "rcu_head",
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.fixup_init = rcuhead_fixup_init,
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.fixup_activate = rcuhead_fixup_activate,
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.fixup_free = rcuhead_fixup_free,
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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_TREE_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
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void do_trace_rcu_torture_read(char *rcutorturename, struct rcu_head *rhp)
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{
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trace_rcu_torture_read(rcutorturename, rhp);
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}
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EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
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#else
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#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
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#endif
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