rcupdate.c

  1 /*
  2  * Read-Copy Update mechanism for mutual exclusion
  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, 2001
 19  *
 20  * Authors: Dipankar Sarma <dipankar@in.ibm.com>
 21  *          Manfred Spraul <manfred@colorfullife.com>
 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  * Papers:
 26  * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
 27  * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
 28  *
 29  * For detailed explanation of Read-Copy Update mechanism see -
 30  *              http://lse.sourceforge.net/locking/rcupdate.html
 31  *
 32  */
 33 #include <linux/types.h>
 34 #include <linux/kernel.h>
 35 #include <linux/init.h>
 36 #include <linux/spinlock.h>
 37 #include <linux/smp.h>
 38 #include <linux/interrupt.h>
 39 #include <linux/sched.h>
 40 #include <asm/atomic.h>
 41 #include <linux/bitops.h>
 42 #include <linux/percpu.h>
 43 #include <linux/notifier.h>
 44 #include <linux/cpu.h>
 45 #include <linux/mutex.h>
 46 #include <linux/module.h>
 47 #include <linux/kernel_stat.h>
 48 #include <linux/hardirq.h>
 49 
 50 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 51 static struct lock_class_key rcu_lock_key;
 52 struct lockdep_map rcu_lock_map =
 53         STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
 54 EXPORT_SYMBOL_GPL(rcu_lock_map);
 55 
 56 static struct lock_class_key rcu_bh_lock_key;
 57 struct lockdep_map rcu_bh_lock_map =
 58         STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
 59 EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
 60 
 61 static struct lock_class_key rcu_sched_lock_key;
 62 struct lockdep_map rcu_sched_lock_map =
 63         STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
 64 EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
 65 #endif
 66 
 67 int rcu_scheduler_active __read_mostly;
 68 EXPORT_SYMBOL_GPL(rcu_scheduler_active);
 69 
 70 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 71 
 72 int debug_lockdep_rcu_enabled(void)
 73 {
 74         return rcu_scheduler_active && debug_locks &&
 75                current->lockdep_recursion == 0;
 76 }
 77 EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
 78 
 79 /**
 80  * rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section?
 81  *
 82  * Check for bottom half being disabled, which covers both the
 83  * CONFIG_PROVE_RCU and not cases.  Note that if someone uses
 84  * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
 85  * will show the situation.
 86  *
 87  * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
 88  */
 89 int rcu_read_lock_bh_held(void)
 90 {
 91         if (!debug_lockdep_rcu_enabled())
 92                 return 1;
 93         return in_softirq();
 94 }
 95 EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
 96 
 97 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 98 
 99 /*
100  * This function is invoked towards the end of the scheduler's initialization
101  * process.  Before this is called, the idle task might contain
102  * RCU read-side critical sections (during which time, this idle
103  * task is booting the system).  After this function is called, the
104  * idle tasks are prohibited from containing RCU read-side critical
105  * sections.
106  */
107 void rcu_scheduler_starting(void)
108 {
109         WARN_ON(num_online_cpus() != 1);
110         WARN_ON(nr_context_switches() > 0);
111         rcu_scheduler_active = 1;
112 }
113 
114 /*
115  * Awaken the corresponding synchronize_rcu() instance now that a
116  * grace period has elapsed.
117  */
118 void wakeme_after_rcu(struct rcu_head  *head)
119 {
120         struct rcu_synchronize *rcu;
121 
122         rcu = container_of(head, struct rcu_synchronize, head);
123         complete(&rcu->completion);
124 }
125 
126 #ifdef CONFIG_PROVE_RCU
127 /*
128  * wrapper function to avoid #include problems.
129  */
130 int rcu_my_thread_group_empty(void)
131 {
132         return thread_group_empty(current);
133 }
134 EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty);
135 #endif /* #ifdef CONFIG_PROVE_RCU */
136
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Linux/kernel/rcupdate.c
