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
  33 extern void rcu_init(void);
  34 extern void rcu_note_context_switch(int cpu);
  35 extern int rcu_needs_cpu(int cpu);
  36 extern void rcu_cpu_stall_reset(void);
  37
  38 /*
  39  * Note a virtualization-based context switch.  This is simply a
  40  * wrapper around rcu_note_context_switch(), which allows TINY_RCU
  41  * to save a few bytes.
  42  */
  43 static inline void rcu_virt_note_context_switch(int cpu)
  44 {
  45         rcu_note_context_switch(cpu);
  46 }
  47
  48 #ifdef CONFIG_TREE_PREEMPT_RCU
  49
  50 extern void exit_rcu(void);
  51
  52 #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
  53
  54 static inline void exit_rcu(void)
  55 {
  56 }
  57
  58 #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
  59
  60 extern void synchronize_rcu_bh(void);
  61 extern void synchronize_sched_expedited(void);
  62 extern void synchronize_rcu_expedited(void);
  63
  64 void kfree_call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
  65
  66 /**
  67  * synchronize_rcu_bh_expedited - Brute-force RCU-bh grace period
  68  *
  69  * Wait for an RCU-bh grace period to elapse, but use a "big hammer"
  70  * approach to force the grace period to end quickly.  This consumes
  71  * significant time on all CPUs and is unfriendly to real-time workloads,
  72  * so is thus not recommended for any sort of common-case code.  In fact,
  73  * if you are using synchronize_rcu_bh_expedited() in a loop, please
  74  * restructure your code to batch your updates, and then use a single
  75  * synchronize_rcu_bh() instead.
  76  *
  77  * Note that it is illegal to call this function while holding any lock
  78  * that is acquired by a CPU-hotplug notifier.  And yes, it is also illegal
  79  * to call this function from a CPU-hotplug notifier.  Failing to observe
  80  * these restriction will result in deadlock.
  81  */
  82 static inline void synchronize_rcu_bh_expedited(void)
  83 {
  84         synchronize_sched_expedited();
  85 }
  86
  87 extern void rcu_barrier(void);
  88 extern void rcu_barrier_bh(void);
  89 extern void rcu_barrier_sched(void);
  90
  91 extern unsigned long rcutorture_testseq;
  92 extern unsigned long rcutorture_vernum;
  93 extern long rcu_batches_completed(void);
  94 extern long rcu_batches_completed_bh(void);
  95 extern long rcu_batches_completed_sched(void);
  96
  97 extern void rcu_force_quiescent_state(void);
  98 extern void rcu_bh_force_quiescent_state(void);
  99 extern void rcu_sched_force_quiescent_state(void);
 100
 101 /* A context switch is a grace period for RCU-sched and RCU-bh. */
 102 static inline int rcu_blocking_is_gp(void)
 103 {
 104         might_sleep();  /* Check for RCU read-side critical section. */
 105         return num_online_cpus() == 1;
 106 }
 107
 108 extern void rcu_scheduler_starting(void);
 109 extern int rcu_scheduler_active __read_mostly;
 110
 111 #endif /* __LINUX_RCUTREE_H */