/* * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition. * * 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, you can access it online at * http://www.gnu.org/licenses/gpl-2.0.html. * * Copyright IBM Corporation, 2008 * * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> * * For detailed explanation of Read-Copy Update mechanism see - *		Documentation/RCU */#include <linux/completion.h>#include <linux/interrupt.h>#include <linux/notifier.h>#include <linux/rcupdate.h>#include <linux/kernel.h>#include <linux/export.h>#include <linux/mutex.h>#include <linux/sched.h>#include <linux/types.h>#include <linux/init.h>#include <linux/time.h>#include <linux/cpu.h>#include <linux/prefetch.h>#include <linux/ftrace_event.h> #include "rcu.h" /* Forward declarations for tiny_plugin.h. */struct rcu_ctrlblk;static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp);static void rcu_process_callbacks(struct softirq_action *unused);static void __call_rcu(struct rcu_head *head,		       void (*func)(struct rcu_head *rcu),		       struct rcu_ctrlblk *rcp); #include "tiny_plugin.h" /* * Enter idle, which is an extended quiescent state if we have fully * entered that mode. */void rcu_idle_enter(void){}EXPORT_SYMBOL_GPL(rcu_idle_enter); /* * Exit an interrupt handler towards idle. */void rcu_irq_exit(void){}EXPORT_SYMBOL_GPL(rcu_irq_exit); /* * Exit idle, so that we are no longer in an extended quiescent state. */void rcu_idle_exit(void){}EXPORT_SYMBOL_GPL(rcu_idle_exit); /* * Enter an interrupt handler, moving away from idle. */void rcu_irq_enter(void){}EXPORT_SYMBOL_GPL(rcu_irq_enter); #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) /* * Test whether RCU thinks that the current CPU is idle. */bool notrace __rcu_is_watching(void){	return true;}EXPORT_SYMBOL(__rcu_is_watching); #endif /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */ /* * Helper function for rcu_sched_qs() and rcu_bh_qs(). * Also irqs are disabled to avoid confusion due to interrupt handlers * invoking call_rcu(). */static int rcu_qsctr_help(struct rcu_ctrlblk *rcp){	RCU_TRACE(reset_cpu_stall_ticks(rcp));	if (rcp->rcucblist != NULL &&	    rcp->donetail != rcp->curtail) {		rcp->donetail = rcp->curtail;		return 1;	} 	return 0;} /* * Record an rcu quiescent state.  And an rcu_bh quiescent state while we * are at it, given that any rcu quiescent state is also an rcu_bh * quiescent state.  Use "+" instead of "||" to defeat short circuiting. */void rcu_sched_qs(void){	unsigned long flags; 	local_irq_save(flags);	if (rcu_qsctr_help(&rcu_sched_ctrlblk) +	    rcu_qsctr_help(&rcu_bh_ctrlblk))		raise_softirq(RCU_SOFTIRQ);	local_irq_restore(flags);} /* * Record an rcu_bh quiescent state. */void rcu_bh_qs(void){	unsigned long flags; 	local_irq_save(flags);	if (rcu_qsctr_help(&rcu_bh_ctrlblk))		raise_softirq(RCU_SOFTIRQ);	local_irq_restore(flags);} /* * Check to see if the scheduling-clock interrupt came from an extended * quiescent state, and, if so, tell RCU about it.  This function must * be called from hardirq context.  It is normally called from the * scheduling-clock interrupt. */void rcu_check_callbacks(int user){	RCU_TRACE(check_cpu_stalls());	if (user)		rcu_sched_qs();	else if (!in_softirq())		rcu_bh_qs();	if (user)		rcu_note_voluntary_context_switch(current);} /* * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure * whose grace period has elapsed. */static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp){	const char *rn = NULL;	struct rcu_head *next, *list;	unsigned long flags;	RCU_TRACE(int cb_count = 0); 	/* If no RCU callbacks ready to invoke, just return. */	if (&rcp->rcucblist == rcp->donetail) {		RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, 0, -1));		RCU_TRACE(trace_rcu_batch_end(rcp->name, 0,					      !!ACCESS_ONCE(rcp->rcucblist),					      need_resched(),					      is_idle_task(current),					      false));		return;	} 	/* Move the ready-to-invoke callbacks to a local list. */	local_irq_save(flags);	RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, rcp->qlen, -1));	list = rcp->rcucblist;	rcp->rcucblist = *rcp->donetail;	*rcp->donetail = NULL;	if (rcp->curtail == rcp->donetail)		rcp->curtail = &rcp->rcucblist;	rcp->donetail = &rcp->rcucblist;	local_irq_restore(flags); 	/* Invoke the callbacks on the local list. */	RCU_TRACE(rn = rcp->name);	while (list) {		next = list->next;		prefetch(next);		debug_rcu_head_unqueue(list);		local_bh_disable();		__rcu_reclaim(rn, list);		local_bh_enable();		list = next;		RCU_TRACE(cb_count++);	}	RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));	RCU_TRACE(trace_rcu_batch_end(rcp->name,				      cb_count, 0, need_resched(),				      is_idle_task(current),				      false));} static void rcu_process_callbacks(struct softirq_action *unused){	__rcu_process_callbacks(&rcu_sched_ctrlblk);	__rcu_process_callbacks(&rcu_bh_ctrlblk);} /* * Wait for a grace period to elapse.  But it is illegal to invoke * synchronize_sched() from within an RCU read-side critical section. * Therefore, any legal call to synchronize_sched() is a quiescent * state, and so on a UP system, synchronize_sched() need do nothing. * Ditto for synchronize_rcu_bh().  (But Lai Jiangshan points out the * benefits of doing might_sleep() to reduce latency.) * * Cool, huh?  (Due to Josh Triplett.) * * But we want to make this a static inline later.  The cond_resched() * currently makes this problematic. */void synchronize_sched(void){	rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&			   !lock_is_held(&rcu_lock_map) &&			   !lock_is_held(&rcu_sched_lock_map),			   "Illegal synchronize_sched() in RCU read-side critical section");	cond_resched();}EXPORT_SYMBOL_GPL(synchronize_sched); /* * Helper function for call_rcu() and call_rcu_bh(). */static void __call_rcu(struct rcu_head *head,		       void (*func)(struct rcu_head *rcu),		       struct rcu_ctrlblk *rcp){	unsigned long flags; 	debug_rcu_head_queue(head);	head->func = func;	head->next = NULL; 	local_irq_save(flags);	*rcp->curtail = head;	rcp->curtail = &head->next;	RCU_TRACE(rcp->qlen++);	local_irq_restore(flags); 	if (unlikely(is_idle_task(current))) {		/* force scheduling for rcu_sched_qs() */		resched_cpu(0);	}} /* * Post an RCU callback to be invoked after the end of an RCU-sched grace * period.  But since we have but one CPU, that would be after any * quiescent state. */void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)){	__call_rcu(head, func, &rcu_sched_ctrlblk);}EXPORT_SYMBOL_GPL(call_rcu_sched); /* * Post an RCU bottom-half callback to be invoked after any subsequent * quiescent state. */void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)){	__call_rcu(head, func, &rcu_bh_ctrlblk);}EXPORT_SYMBOL_GPL(call_rcu_bh); void __init rcu_init(void){	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);	RCU_TRACE(reset_cpu_stall_ticks(&rcu_sched_ctrlblk));	RCU_TRACE(reset_cpu_stall_ticks(&rcu_bh_ctrlblk)); 	rcu_early_boot_tests();}