kernel/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
  49 #ifdef CONFIG_DEBUG_LOCK_ALLOC
  50 static struct lock_class_key rcu_lock_key;
  51 struct lockdep_map rcu_lock_map =
  52         STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
  53 EXPORT_SYMBOL_GPL(rcu_lock_map);
  54
  55 static struct lock_class_key rcu_bh_lock_key;
  56 struct lockdep_map rcu_bh_lock_map =
  57         STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
  58 EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
  59
  60 static struct lock_class_key rcu_sched_lock_key;
  61 struct lockdep_map rcu_sched_lock_map =
  62         STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
  63 EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
  64 #endif
  65
  66 int rcu_scheduler_active __read_mostly;
  67 EXPORT_SYMBOL_GPL(rcu_scheduler_active);
  68
  69 /*
  70  * This function is invoked towards the end of the scheduler's initialization
  71  * process.  Before this is called, the idle task might contain
  72  * RCU read-side critical sections (during which time, this idle
  73  * task is booting the system).  After this function is called, the
  74  * idle tasks are prohibited from containing RCU read-side critical
  75  * sections.
  76  */
  77 void rcu_scheduler_starting(void)
  78 {
  79         WARN_ON(num_online_cpus() != 1);
  80         WARN_ON(nr_context_switches() > 0);
  81         rcu_scheduler_active = 1;
  82 }
  83
  84 /*
  85  * Awaken the corresponding synchronize_rcu() instance now that a
  86  * grace period has elapsed.
  87  */
  88 void wakeme_after_rcu(struct rcu_head  *head)
  89 {
  90         struct rcu_synchronize *rcu;
  91
  92         rcu = container_of(head, struct rcu_synchronize, head);
  93         complete(&rcu->completion);
  94 }