LXR linux/include/linux/rcutree.h

   1/*
   2 * Read-Copy Update mechanism for mutual exclusion (tree-based version)
   3 *
   4 * This program is free software; you can redistribute it and/or modify
   5 * it under the terms of the GNU General Public License as published by
   6 * the Free Software Foundation; either version 2 of the License, or
   7 * (at your option) any later version.
   8 *
   9 * This program is distributed in the hope that it will be useful,
  10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 * GNU General Public License for more details.
  13 *
  14 * You should have received a copy of the GNU General Public License
  15 * along with this program; if not, write to the Free Software
  16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17 *
  18 * Copyright IBM Corporation, 2008
  19 *
  20 * Author: Dipankar Sarma <dipankar@in.ibm.com>
  21 *         Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical algorithm
  22 *
  23 * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
  24 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
  25 *
  26 * For detailed explanation of Read-Copy Update mechanism see -
  27 *      Documentation/RCU
  28 */
  29
  30#ifndef __LINUX_RCUTREE_H
  31#define __LINUX_RCUTREE_H
  32
  33struct notifier_block;
  34
  35extern void rcu_sched_qs(int cpu);
  36extern void rcu_bh_qs(int cpu);
  37extern void rcu_note_context_switch(int cpu);
  38extern int rcu_needs_cpu(int cpu);
  39
  40#ifdef CONFIG_TREE_PREEMPT_RCU
  41
  42extern void __rcu_read_lock(void);
  43extern void __rcu_read_unlock(void);
  44extern void synchronize_rcu(void);
  45extern void exit_rcu(void);
  46
  47/*
  48 * Defined as macro as it is a very low level header
  49 * included from areas that don't even know about current
  50 */
  51#define rcu_preempt_depth() (current->rcu_read_lock_nesting)
  52
  53#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
  54
  55static inline void __rcu_read_lock(void)
  56{
  57        preempt_disable();
  58}
  59
  60static inline void __rcu_read_unlock(void)
  61{
  62        preempt_enable();
  63}
  64
  65#define synchronize_rcu synchronize_sched
  66
  67static inline void exit_rcu(void)
  68{
  69}
  70
  71static inline int rcu_preempt_depth(void)
  72{
  73        return 0;
  74}
  75
  76#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
  77
  78static inline void __rcu_read_lock_bh(void)
  79{
  80        local_bh_disable();
  81}
  82static inline void __rcu_read_unlock_bh(void)
  83{
  84        local_bh_enable();
  85}
  86
  87extern void call_rcu_sched(struct rcu_head *head,
  88                           void (*func)(struct rcu_head *rcu));
  89extern void synchronize_rcu_bh(void);
  90extern void synchronize_sched(void);
  91extern void synchronize_rcu_expedited(void);
  92
  93static inline void synchronize_rcu_bh_expedited(void)
  94{
  95        synchronize_sched_expedited();
  96}
  97
  98extern void rcu_check_callbacks(int cpu, int user);
  99
 100extern long rcu_batches_completed(void);
 101extern long rcu_batches_completed_bh(void);
 102extern long rcu_batches_completed_sched(void);
 103extern void rcu_force_quiescent_state(void);
 104extern void rcu_bh_force_quiescent_state(void);
 105extern void rcu_sched_force_quiescent_state(void);
 106
 107#ifdef CONFIG_NO_HZ
 108void rcu_enter_nohz(void);
 109void rcu_exit_nohz(void);
 110#else /* CONFIG_NO_HZ */
 111static inline void rcu_enter_nohz(void)
 112{
 113}
 114static inline void rcu_exit_nohz(void)
 115{
 116}
 117#endif /* CONFIG_NO_HZ */
 118
 119/* A context switch is a grace period for RCU-sched and RCU-bh. */
 120static inline int rcu_blocking_is_gp(void)
 121{
 122        return num_online_cpus() == 1;
 123}
 124
 125extern void rcu_scheduler_starting(void);
 126extern int rcu_scheduler_active __read_mostly;
 127
 128#endif /* __LINUX_RCUTREE_H */
 129