kernel/rcutiny.c - kernel/msm-4.19 - 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>

 /* Global control variables for rcupdate callback mechanism. */
 struct rcu_ctrlblk {
 	struct rcu_head *rcucblist;	/* List of pending callbacks (CBs). */
 	struct rcu_head **donetail;	/* ->next pointer of last "done" CB. */
 	struct rcu_head **curtail;	/* ->next pointer of last CB. */
 };

 /* Definition for rcupdate control block. */
 static struct rcu_ctrlblk rcu_sched_ctrlblk = {
 	.donetail	= &rcu_sched_ctrlblk.rcucblist,
 	.curtail	= &rcu_sched_ctrlblk.rcucblist,
 };

 static struct rcu_ctrlblk rcu_bh_ctrlblk = {
 	.donetail	= &rcu_bh_ctrlblk.rcucblist,
 	.curtail	= &rcu_bh_ctrlblk.rcucblist,
 };

 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 int rcu_scheduler_active __read_mostly;
 EXPORT_SYMBOL_GPL(rcu_scheduler_active);
 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

 #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_qsctr_inc() and rcu_bh_qsctr_inc().
  * Also disable irqs to avoid confusion due to interrupt handlers
  * invoking call_rcu().
  */
 static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
 {
 	unsigned long flags;

 	local_irq_save(flags);
 	if (rcp->rcucblist != NULL &&
 	    rcp->donetail != rcp->curtail) {
 		rcp->donetail = rcp->curtail;
 		local_irq_restore(flags);
 		return 1;
 	}
 	local_irq_restore(flags);

 	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(int cpu)
 {
 	if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
 	    rcu_qsctr_help(&rcu_bh_ctrlblk))
 		raise_softirq(RCU_SOFTIRQ);
 }

 /*
  * Record an rcu_bh quiescent state.
  */
 void rcu_bh_qs(int cpu)
 {
 	if (rcu_qsctr_help(&rcu_bh_ctrlblk))
 		raise_softirq(RCU_SOFTIRQ);
 }

 /*
  * 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);
 }

 /*
  * Helper function for rcu_process_callbacks() that operates on the
  * specified rcu_ctrlkblk structure.
  */
 static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
 {
 	struct rcu_head *next, *list;
 	unsigned long flags;

 	/* 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;
 	rcp->donetail = &rcp->rcucblist;
 	local_irq_restore(flags);

 	/* Invoke the callbacks on the local list. */
 	while (list) {
 		next = list->next;
 		prefetch(next);
 		list->func(list);
 		list = next;
 	}
 }

 /*
  * Invoke any callbacks whose grace period has completed.
  */
 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)
 {
 	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;

 	head->func = func;
 	head->next = NULL;

 	local_irq_save(flags);
 	*rcp->curtail = head;
 	rcp->curtail = &head->next;
 	local_irq_restore(flags);
 }

 /*
  * Post an RCU callback to be invoked after the end of an RCU grace
  * period.  But since we have but one CPU, that would be after any
  * quiescent state.
  */
 void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
 {
 	__call_rcu(head, func, &rcu_sched_ctrlblk);
 }
 EXPORT_SYMBOL_GPL(call_rcu);

 /*
  * 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(void)
 {
 	struct rcu_synchronize rcu;

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

 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);

 void __init rcu_init(void)
 {
 	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
 }

 #include "rcutiny_plugin.h"
	/*
	* 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>

	/* Global control variables for rcupdate callback mechanism. */
	struct rcu_ctrlblk {
	struct rcu_head rcucblist; / List of pending callbacks (CBs). */
	struct rcu_head *donetail; / ->next pointer of last "done" CB. */
	struct rcu_head *curtail; / ->next pointer of last CB. */
	};

	/* Definition for rcupdate control block. */
	static struct rcu_ctrlblk rcu_sched_ctrlblk = {
	.donetail = &rcu_sched_ctrlblk.rcucblist,
	.curtail = &rcu_sched_ctrlblk.rcucblist,
	};

	static struct rcu_ctrlblk rcu_bh_ctrlblk = {
	.donetail = &rcu_bh_ctrlblk.rcucblist,
	.curtail = &rcu_bh_ctrlblk.rcucblist,
	};

	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	int rcu_scheduler_active __read_mostly;
	EXPORT_SYMBOL_GPL(rcu_scheduler_active);
	#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

	#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_qsctr_inc() and rcu_bh_qsctr_inc().
	* Also disable irqs to avoid confusion due to interrupt handlers
	* invoking call_rcu().
	*/
	static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
	{
	unsigned long flags;

	local_irq_save(flags);
	if (rcp->rcucblist != NULL &&
	rcp->donetail != rcp->curtail) {
	rcp->donetail = rcp->curtail;
	local_irq_restore(flags);
	return 1;
	}
	local_irq_restore(flags);

	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(int cpu)
	{
	if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
	rcu_qsctr_help(&rcu_bh_ctrlblk))
	raise_softirq(RCU_SOFTIRQ);
	}

	/*
	* Record an rcu_bh quiescent state.
	*/
	void rcu_bh_qs(int cpu)
	{
	if (rcu_qsctr_help(&rcu_bh_ctrlblk))
	raise_softirq(RCU_SOFTIRQ);
	}

	/*
	* 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);
	}

	/*
	* Helper function for rcu_process_callbacks() that operates on the
	* specified rcu_ctrlkblk structure.
	*/
	static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
	{
	struct rcu_head next, list;
	unsigned long flags;

	/* 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;
	rcp->donetail = &rcp->rcucblist;
	local_irq_restore(flags);

	/* Invoke the callbacks on the local list. */
	while (list) {
	next = list->next;
	prefetch(next);
	list->func(list);
	list = next;
	}
	}

	/*
	* Invoke any callbacks whose grace period has completed.
	*/
	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)
	{
	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;

	head->func = func;
	head->next = NULL;

	local_irq_save(flags);
	*rcp->curtail = head;
	rcp->curtail = &head->next;
	local_irq_restore(flags);
	}

	/*
	* Post an RCU callback to be invoked after the end of an RCU grace
	* period. But since we have but one CPU, that would be after any
	* quiescent state.
	*/
	void call_rcu(struct rcu_head head, void (func)(struct rcu_head *rcu))
	{
	__call_rcu(head, func, &rcu_sched_ctrlblk);
	}
	EXPORT_SYMBOL_GPL(call_rcu);

	/*
	* 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(void)
	{
	struct rcu_synchronize rcu;

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

	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);

	void __init rcu_init(void)
	{
	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
	}

	#include "rcutiny_plugin.h"