/* * 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/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> #ifdef CONFIG_RCU_TRACE#include <trace/events/rcu.h>#endif /* #else #ifdef CONFIG_RCU_TRACE */ #include "rcu.h" /* Forward declarations for rcutiny_plugin.h. */struct rcu_ctrlblk;static void invoke_rcu_callbacks(void);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 "rcutiny_plugin.h" static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; /* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */static void rcu_idle_enter_common(long long newval){	if (newval) {		RCU_TRACE(trace_rcu_dyntick("--=",					    rcu_dynticks_nesting, newval));		rcu_dynticks_nesting = newval;		return;	}	RCU_TRACE(trace_rcu_dyntick("Start", rcu_dynticks_nesting, newval));	if (!is_idle_task(current)) {		struct task_struct *idle = idle_task(smp_processor_id()); 		RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",					    rcu_dynticks_nesting, newval));		ftrace_dump(DUMP_ALL);		WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",			  current->pid, current->comm,			  idle->pid, idle->comm); /* must be idle task! */	}	rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */	barrier();	rcu_dynticks_nesting = newval;} /* * Enter idle, 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_idle_enter(void){	unsigned long flags;	long long newval; 	local_irq_save(flags);	WARN_ON_ONCE((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) == 0);	if ((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) ==	    DYNTICK_TASK_NEST_VALUE)		newval = 0;	else		newval = rcu_dynticks_nesting - DYNTICK_TASK_NEST_VALUE;	rcu_idle_enter_common(newval);	local_irq_restore(flags);}EXPORT_SYMBOL_GPL(rcu_idle_enter); /* * Exit an interrupt handler towards idle. */void rcu_irq_exit(void){	unsigned long flags;	long long newval; 	local_irq_save(flags);	newval = rcu_dynticks_nesting - 1;	WARN_ON_ONCE(newval < 0);	rcu_idle_enter_common(newval);	local_irq_restore(flags);}EXPORT_SYMBOL_GPL(rcu_irq_exit); /* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */static void rcu_idle_exit_common(long long oldval){	if (oldval) {		RCU_TRACE(trace_rcu_dyntick("++=",					    oldval, rcu_dynticks_nesting));		return;	}	RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting));	if (!is_idle_task(current)) {		struct task_struct *idle = idle_task(smp_processor_id()); 		RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",			  oldval, rcu_dynticks_nesting));		ftrace_dump(DUMP_ALL);		WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",			  current->pid, current->comm,			  idle->pid, idle->comm); /* must be idle task! */	}} /* * Exit idle, so that we are no longer in an extended quiescent state. */void rcu_idle_exit(void){	unsigned long flags;	long long oldval; 	local_irq_save(flags);	oldval = rcu_dynticks_nesting;	WARN_ON_ONCE(rcu_dynticks_nesting < 0);	if (rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK)		rcu_dynticks_nesting += DYNTICK_TASK_NEST_VALUE;	else		rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;	rcu_idle_exit_common(oldval);	local_irq_restore(flags);}EXPORT_SYMBOL_GPL(rcu_idle_exit); /* * Enter an interrupt handler, moving away from idle. */void rcu_irq_enter(void){	unsigned long flags;	long long oldval; 	local_irq_save(flags);	oldval = rcu_dynticks_nesting;	rcu_dynticks_nesting++;	WARN_ON_ONCE(rcu_dynticks_nesting == 0);	rcu_idle_exit_common(oldval);	local_irq_restore(flags);}EXPORT_SYMBOL_GPL(rcu_irq_enter); #ifdef CONFIG_DEBUG_LOCK_ALLOC /* * Test whether RCU thinks that the current CPU is idle. */int rcu_is_cpu_idle(void){	return !rcu_dynticks_nesting;}EXPORT_SYMBOL(rcu_is_cpu_idle); #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ /* * Test whether the current CPU was interrupted from idle.  Nested * interrupts don't count, we must be running at the first interrupt * level. */int rcu_is_cpu_rrupt_from_idle(void){	return rcu_dynticks_nesting <= 1;} /* * 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;} /* * 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_callbacks();	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_callbacks();	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 cpu, int user){	if (user || rcu_is_cpu_rrupt_from_idle())		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){	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),					      rcu_is_callbacks_kthread()));		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;	rcu_preempt_remove_callbacks(rcp);	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),				      rcu_is_callbacks_kthread()));} static void rcu_process_callbacks(struct softirq_action *unused){	__rcu_process_callbacks(&rcu_sched_ctrlblk);	__rcu_process_callbacks(&rcu_bh_ctrlblk);	rcu_preempt_process_callbacks();} /* * 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);} /* * 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);