kernel/rcutiny.c - kernel/msm-4.9 - Gitiles

 /*
  * 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, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  *
  * 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/moduleparam.h>
 #include <linux/completion.h>
 #include <linux/interrupt.h>
 #include <linux/notifier.h>
 #include <linux/rcupdate.h>
 #include <linux/kernel.h>
 #include <linux/module.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>

 /* Controls for rcu_kthread() kthread, replacing RCU_SOFTIRQ used previously. */
 static struct task_struct *rcu_kthread_task;
 static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq);
 static unsigned long have_rcu_kthread_work;

 /* Forward declarations for rcutiny_plugin.h. */
 struct rcu_ctrlblk;
 static void invoke_rcu_kthread(void);
 static void rcu_process_callbacks(struct rcu_ctrlblk *rcp);
 static int rcu_kthread(void *arg);
 static void __call_rcu(struct rcu_head *head,
 		       void (*func)(struct rcu_head *rcu),
 		       struct rcu_ctrlblk *rcp);

 #include "rcutiny_plugin.h"

 #ifdef CONFIG_NO_HZ

 static long rcu_dynticks_nesting = 1;

 /*
  * Enter dynticks-idle mode, which is an extended quiescent state
  * if we have fully entered that mode (i.e., if the new value of
  * dynticks_nesting is zero).
  */
 void rcu_enter_nohz(void)
 {
 	if (--rcu_dynticks_nesting == 0)
 		rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
 }

 /*
  * Exit dynticks-idle mode, so that we are no longer in an extended
  * quiescent state.
  */
 void rcu_exit_nohz(void)
 {
 	rcu_dynticks_nesting++;
 }

 #endif /* #ifdef CONFIG_NO_HZ */

 /*
  * 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)
 {
 	if (rcp->rcucblist != NULL &&
 	    rcp->donetail != rcp->curtail) {
 		rcp->donetail = rcp->curtail;
 		return 1;
 	}

 	return 0;
 }

 /*
  * Wake up rcu_kthread() to process callbacks now eligible for invocation
  * or to boost readers.
  */
 static void invoke_rcu_kthread(void)
 {
 	have_rcu_kthread_work = 1;
 	wake_up(&rcu_kthread_wq);
 }

 /*
  * 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(int cpu)
 {
 	unsigned long flags;

 	local_irq_save(flags);
 	if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
 	    rcu_qsctr_help(&rcu_bh_ctrlblk))
 		invoke_rcu_kthread();
 	local_irq_restore(flags);
 }

 /*
  * Record an rcu_bh quiescent state.
  */
 void rcu_bh_qs(int cpu)
 {
 	unsigned long flags;

 	local_irq_save(flags);
 	if (rcu_qsctr_help(&rcu_bh_ctrlblk))
 		invoke_rcu_kthread();
 	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.
  */
 void rcu_check_callbacks(int cpu, int user)
 {
 	if (user ||
 	    (idle_cpu(cpu) &&
 	     !in_softirq() &&
 	     hardirq_count() <= (1 << HARDIRQ_SHIFT)))
 		rcu_sched_qs(cpu);
 	else if (!in_softirq())
 		rcu_bh_qs(cpu);
 	rcu_preempt_check_callbacks();
 }

 /*
  * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
  * whose grace period has elapsed.
  */
 static void rcu_process_callbacks(struct rcu_ctrlblk *rcp)
 {
 	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)
 		return;

 	/* Move the ready-to-invoke callbacks to a local list. */
 	local_irq_save(flags);
 	list = rcp->rcucblist;
 	rcp->rcucblist = *rcp->donetail;
 	*rcp->donetail = NULL;
 	if (rcp->curtail == rcp->donetail)
 		rcp->curtail = &rcp->rcucblist;
 	rcu_preempt_remove_callbacks(rcp);
 	rcp->donetail = &rcp->rcucblist;
 	local_irq_restore(flags);

 	/* Invoke the callbacks on the local list. */
 	while (list) {
 		next = list->next;
 		prefetch(next);
 		debug_rcu_head_unqueue(list);
 		local_bh_disable();
 		__rcu_reclaim(list);
 		local_bh_enable();
 		list = next;
 		RCU_TRACE(cb_count++);
 	}
 	RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));
 }

 /*
  * This kthread invokes RCU callbacks whose grace periods have
  * elapsed.  It is awakened as needed, and takes the place of the
  * RCU_SOFTIRQ that was used previously for this purpose.
  * This is a kthread, but it is never stopped, at least not until
  * the system goes down.
  */
 static int rcu_kthread(void *arg)
 {
 	unsigned long work;
 	unsigned long morework;
 	unsigned long flags;

 	for (;;) {
 		wait_event_interruptible(rcu_kthread_wq,
 					 have_rcu_kthread_work != 0);
 		morework = rcu_boost();
 		local_irq_save(flags);
 		work = have_rcu_kthread_work;
 		have_rcu_kthread_work = morework;
 		local_irq_restore(flags);
 		if (work) {
 			rcu_process_callbacks(&rcu_sched_ctrlblk);
 			rcu_process_callbacks(&rcu_bh_ctrlblk);
 			rcu_preempt_process_callbacks();
 		}
 		schedule_timeout_interruptible(1); /* Leave CPU for others. */
 	}

 	return 0;  /* Not reached, but needed to shut gcc up. */
 }

 /*
  * 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)
 {
 	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);
 }

 /*
  * 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 rcu_barrier_bh(void)
 {
 	struct rcu_synchronize rcu;

 	init_rcu_head_on_stack(&rcu.head);
 	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);
 	destroy_rcu_head_on_stack(&rcu.head);
 }
 EXPORT_SYMBOL_GPL(rcu_barrier_bh);

 void rcu_barrier_sched(void)
 {
 	struct rcu_synchronize rcu;

 	init_rcu_head_on_stack(&rcu.head);
 	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);
 	destroy_rcu_head_on_stack(&rcu.head);
 }
 EXPORT_SYMBOL_GPL(rcu_barrier_sched);

 /*
  * Spawn the kthread that invokes RCU callbacks.
  */
 static int __init rcu_spawn_kthreads(void)
 {
 	struct sched_param sp;

 	rcu_kthread_task = kthread_run(rcu_kthread, NULL, "rcu_kthread");
 	sp.sched_priority = RCU_BOOST_PRIO;
 	sched_setscheduler_nocheck(rcu_kthread_task, SCHED_FIFO, &sp);
 	return 0;
 }
 early_initcall(rcu_spawn_kthreads);
	/*
	* 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, write to the Free Software
	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	*
	* 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/moduleparam.h>
	#include <linux/completion.h>
	#include <linux/interrupt.h>
	#include <linux/notifier.h>
	#include <linux/rcupdate.h>
	#include <linux/kernel.h>
	#include <linux/module.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>

	/* Controls for rcu_kthread() kthread, replacing RCU_SOFTIRQ used previously. */
	static struct task_struct *rcu_kthread_task;
	static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq);
	static unsigned long have_rcu_kthread_work;

	/* Forward declarations for rcutiny_plugin.h. */
	struct rcu_ctrlblk;
	static void invoke_rcu_kthread(void);
	static void rcu_process_callbacks(struct rcu_ctrlblk *rcp);
	static int rcu_kthread(void *arg);
	static void __call_rcu(struct rcu_head *head,
	void (func)(struct rcu_head rcu),
	struct rcu_ctrlblk *rcp);

	#include "rcutiny_plugin.h"

	#ifdef CONFIG_NO_HZ

	static long rcu_dynticks_nesting = 1;

	/*
	* Enter dynticks-idle mode, which is an extended quiescent state
	* if we have fully entered that mode (i.e., if the new value of
	* dynticks_nesting is zero).
	*/
	void rcu_enter_nohz(void)
	{
	if (--rcu_dynticks_nesting == 0)
	rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
	}

	/*
	* Exit dynticks-idle mode, so that we are no longer in an extended
	* quiescent state.
	*/
	void rcu_exit_nohz(void)
	{
	rcu_dynticks_nesting++;
	}

	#endif /* #ifdef CONFIG_NO_HZ */

	/*
	* 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)
	{
	if (rcp->rcucblist != NULL &&
	rcp->donetail != rcp->curtail) {
	rcp->donetail = rcp->curtail;
	return 1;
	}

	return 0;
	}

	/*
	* Wake up rcu_kthread() to process callbacks now eligible for invocation
	* or to boost readers.
	*/
	static void invoke_rcu_kthread(void)
	{
	have_rcu_kthread_work = 1;
	wake_up(&rcu_kthread_wq);
	}

	/*
	* 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(int cpu)
	{
	unsigned long flags;

	local_irq_save(flags);
	if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
	rcu_qsctr_help(&rcu_bh_ctrlblk))
	invoke_rcu_kthread();
	local_irq_restore(flags);
	}

	/*
	* Record an rcu_bh quiescent state.
	*/
	void rcu_bh_qs(int cpu)
	{
	unsigned long flags;

	local_irq_save(flags);
	if (rcu_qsctr_help(&rcu_bh_ctrlblk))
	invoke_rcu_kthread();
	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.
	*/
	void rcu_check_callbacks(int cpu, int user)
	{
	if (user \|\|
	(idle_cpu(cpu) &&
	!in_softirq() &&
	hardirq_count() <= (1 << HARDIRQ_SHIFT)))
	rcu_sched_qs(cpu);
	else if (!in_softirq())
	rcu_bh_qs(cpu);
	rcu_preempt_check_callbacks();
	}

	/*
	* Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
	* whose grace period has elapsed.
	*/
	static void rcu_process_callbacks(struct rcu_ctrlblk *rcp)
	{
	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)
	return;

	/* Move the ready-to-invoke callbacks to a local list. */
	local_irq_save(flags);
	list = rcp->rcucblist;
	rcp->rcucblist = *rcp->donetail;
	*rcp->donetail = NULL;
	if (rcp->curtail == rcp->donetail)
	rcp->curtail = &rcp->rcucblist;
	rcu_preempt_remove_callbacks(rcp);
	rcp->donetail = &rcp->rcucblist;
	local_irq_restore(flags);

	/* Invoke the callbacks on the local list. */
	while (list) {
	next = list->next;
	prefetch(next);
	debug_rcu_head_unqueue(list);
	local_bh_disable();
	__rcu_reclaim(list);
	local_bh_enable();
	list = next;
	RCU_TRACE(cb_count++);
	}
	RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));
	}

	/*
	* This kthread invokes RCU callbacks whose grace periods have
	* elapsed. It is awakened as needed, and takes the place of the
	* RCU_SOFTIRQ that was used previously for this purpose.
	* This is a kthread, but it is never stopped, at least not until
	* the system goes down.
	*/
	static int rcu_kthread(void *arg)
	{
	unsigned long work;
	unsigned long morework;
	unsigned long flags;

	for (;;) {
	wait_event_interruptible(rcu_kthread_wq,
	have_rcu_kthread_work != 0);
	morework = rcu_boost();
	local_irq_save(flags);
	work = have_rcu_kthread_work;
	have_rcu_kthread_work = morework;
	local_irq_restore(flags);
	if (work) {
	rcu_process_callbacks(&rcu_sched_ctrlblk);
	rcu_process_callbacks(&rcu_bh_ctrlblk);
	rcu_preempt_process_callbacks();
	}
	schedule_timeout_interruptible(1); /* Leave CPU for others. */
	}

	return 0; /* Not reached, but needed to shut gcc up. */
	}

	/*
	* 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)
	{
	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);
	}

	/*
	* 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 rcu_barrier_bh(void)
	{
	struct rcu_synchronize rcu;

	init_rcu_head_on_stack(&rcu.head);
	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);
	destroy_rcu_head_on_stack(&rcu.head);
	}
	EXPORT_SYMBOL_GPL(rcu_barrier_bh);

	void rcu_barrier_sched(void)
	{
	struct rcu_synchronize rcu;

	init_rcu_head_on_stack(&rcu.head);
	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);
	destroy_rcu_head_on_stack(&rcu.head);
	}
	EXPORT_SYMBOL_GPL(rcu_barrier_sched);

	/*
	* Spawn the kthread that invokes RCU callbacks.
	*/
	static int __init rcu_spawn_kthreads(void)
	{
	struct sched_param sp;

	rcu_kthread_task = kthread_run(rcu_kthread, NULL, "rcu_kthread");
	sp.sched_priority = RCU_BOOST_PRIO;
	sched_setscheduler_nocheck(rcu_kthread_task, SCHED_FIFO, &sp);
	return 0;
	}
	early_initcall(rcu_spawn_kthreads);