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* Read-Copy Update mechanism for mutual exclusion (tree-based version)
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
* Copyright IBM Corporation, 2008
* Author: Dipankar Sarma <>
* Paul E. McKenney <> Hierarchical algorithm
* Based on the original work by Paul McKenney <>
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
* For detailed explanation of Read-Copy Update mechanism see -
* Documentation/RCU
struct notifier_block;
extern void rcu_sched_qs(int cpu);
extern void rcu_bh_qs(int cpu);
extern void rcu_note_context_switch(int cpu);
extern int rcu_needs_cpu(int cpu);
extern void __rcu_read_lock(void);
extern void __rcu_read_unlock(void);
extern void synchronize_rcu(void);
extern void exit_rcu(void);
* Defined as macro as it is a very low level header
* included from areas that don't even know about current
#define rcu_preempt_depth() (current->rcu_read_lock_nesting)
#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
static inline void __rcu_read_lock(void)
static inline void __rcu_read_unlock(void)
#define synchronize_rcu synchronize_sched
static inline void exit_rcu(void)
static inline int rcu_preempt_depth(void)
return 0;
#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
static inline void __rcu_read_lock_bh(void)
static inline void __rcu_read_unlock_bh(void)
extern void call_rcu_sched(struct rcu_head *head,
void (*func)(struct rcu_head *rcu));
extern void synchronize_rcu_bh(void);
extern void synchronize_sched(void);
extern void synchronize_rcu_expedited(void);
static inline void synchronize_rcu_bh_expedited(void)
extern void rcu_check_callbacks(int cpu, int user);
extern long rcu_batches_completed(void);
extern long rcu_batches_completed_bh(void);
extern long rcu_batches_completed_sched(void);
extern void rcu_force_quiescent_state(void);
extern void rcu_bh_force_quiescent_state(void);
extern void rcu_sched_force_quiescent_state(void);
void rcu_enter_nohz(void);
void rcu_exit_nohz(void);
#else /* CONFIG_NO_HZ */
static inline void rcu_enter_nohz(void)
static inline void rcu_exit_nohz(void)
#endif /* CONFIG_NO_HZ */
/* A context switch is a grace period for RCU-sched and RCU-bh. */
static inline int rcu_blocking_is_gp(void)
return num_online_cpus() == 1;
extern void rcu_scheduler_starting(void);
extern int rcu_scheduler_active __read_mostly;
#endif /* __LINUX_RCUTREE_H */