/* * Read-Copy Update mechanism for mutual exclusion * * 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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * 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, 2001 * * Authors: Dipankar Sarma <dipankar@in.ibm.com> *	    Manfred Spraul <manfred@colorfullife.com> * * Based on the original work by Paul McKenney <paulmck@us.ibm.com> * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. * Papers: * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) * * For detailed explanation of Read-Copy Update mechanism see - *		http://lse.sourceforge.net/locking/rcupdate.html * */#include <linux/types.h>#include <linux/kernel.h>#include <linux/init.h>#include <linux/spinlock.h>#include <linux/smp.h>#include <linux/interrupt.h>#include <linux/sched.h>#include <asm/atomic.h>#include <linux/bitops.h>#include <linux/percpu.h>#include <linux/notifier.h>#include <linux/cpu.h>#include <linux/mutex.h>#include <linux/module.h>#include <linux/kernel_stat.h> #ifdef CONFIG_DEBUG_LOCK_ALLOCstatic struct lock_class_key rcu_lock_key;struct lockdep_map rcu_lock_map =	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);EXPORT_SYMBOL_GPL(rcu_lock_map);#endif int rcu_scheduler_active __read_mostly; /* * Awaken the corresponding synchronize_rcu() instance now that a * grace period has elapsed. */void wakeme_after_rcu(struct rcu_head  *head){	struct rcu_synchronize *rcu; 	rcu = container_of(head, struct rcu_synchronize, head);	complete(&rcu->completion);} #ifdef CONFIG_TREE_PREEMPT_RCU /** * synchronize_rcu - wait until a grace period has elapsed. * * Control will return to the caller some time after a full grace * period has elapsed, in other words after all currently executing RCU * read-side critical sections have completed.  RCU read-side critical * sections are delimited by rcu_read_lock() and rcu_read_unlock(), * and may be nested. */void synchronize_rcu(void){	struct rcu_synchronize rcu; 	if (!rcu_scheduler_active)		return; 	init_completion(&rcu.completion);	/* Will wake me after RCU finished. */	call_rcu(&rcu.head, wakeme_after_rcu);	/* Wait for it. */	wait_for_completion(&rcu.completion);}EXPORT_SYMBOL_GPL(synchronize_rcu); #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ /** * synchronize_sched - wait until an rcu-sched grace period has elapsed. * * Control will return to the caller some time after a full rcu-sched * grace period has elapsed, in other words after all currently executing * rcu-sched read-side critical sections have completed.   These read-side * critical sections are delimited by rcu_read_lock_sched() and * rcu_read_unlock_sched(), and may be nested.  Note that preempt_disable(), * local_irq_disable(), and so on may be used in place of * rcu_read_lock_sched(). * * This means that all preempt_disable code sequences, including NMI and * hardware-interrupt handlers, in progress on entry will have completed * before this primitive returns.  However, this does not guarantee that * softirq handlers will have completed, since in some kernels, these * handlers can run in process context, and can block. * * This primitive provides the guarantees made by the (now removed) * synchronize_kernel() API.  In contrast, synchronize_rcu() only * guarantees that rcu_read_lock() sections will have completed. * In "classic RCU", these two guarantees happen to be one and * the same, but can differ in realtime RCU implementations. */void synchronize_sched(void){	struct rcu_synchronize rcu; 	if (rcu_blocking_is_gp())		return; 	init_completion(&rcu.completion);	/* Will wake me after RCU finished. */	call_rcu_sched(&rcu.head, wakeme_after_rcu);	/* Wait for it. */	wait_for_completion(&rcu.completion);}EXPORT_SYMBOL_GPL(synchronize_sched); /** * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. * * Control will return to the caller some time after a full rcu_bh grace * period has elapsed, in other words after all currently executing rcu_bh * read-side critical sections have completed.  RCU read-side critical * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), * and may be nested. */void synchronize_rcu_bh(void){	struct rcu_synchronize rcu; 	if (rcu_blocking_is_gp())		return; 	init_completion(&rcu.completion);	/* Will wake me after RCU finished. */	call_rcu_bh(&rcu.head, wakeme_after_rcu);	/* Wait for it. */	wait_for_completion(&rcu.completion);}EXPORT_SYMBOL_GPL(synchronize_rcu_bh); static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,		unsigned long action, void *hcpu){	return rcu_cpu_notify(self, action, hcpu);} void __init rcu_init(void){	int i; 	__rcu_init();	cpu_notifier(rcu_barrier_cpu_hotplug, 0); 	/*	 * We don't need protection against CPU-hotplug here because	 * this is called early in boot, before either interrupts	 * or the scheduler are operational.	 */	for_each_online_cpu(i)		rcu_barrier_cpu_hotplug(NULL, CPU_UP_PREPARE, (void *)(long)i);} void rcu_scheduler_starting(void){	WARN_ON(num_online_cpus() != 1);	WARN_ON(nr_context_switches() > 0);	rcu_scheduler_active = 1;}