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Commit 16e30811 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
Browse files

rcu: Fix synchronize_rcu() for TREE_PREEMPT_RCU 



The redirection of synchronize_sched() to synchronize_rcu() was
appropriate for TREE_RCU, but not for TREE_PREEMPT_RCU.

Fix this by creating an underlying synchronize_sched().  TREE_RCU
then redirects synchronize_rcu() to synchronize_sched(), while
TREE_PREEMPT_RCU has its own version of synchronize_rcu().

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
LKML-Reference: <12528585111916-git-send-email->
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent c3422bea

include/linux/rcupdate.h

+5 −18
Original line number Diff line number Diff line
@@ -52,8 +52,13 @@ struct rcu_head { 
};



/* Exported common interfaces */

#ifdef CONFIG_TREE_PREEMPT_RCU

extern void synchronize_rcu(void);

#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */

#define synchronize_rcu synchronize_sched

#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */

extern void synchronize_rcu_bh(void);

extern void synchronize_sched(void);

extern void rcu_barrier(void);

extern void rcu_barrier_bh(void);

extern void rcu_barrier_sched(void);
@@ -261,24 +266,6 @@ struct rcu_synchronize { 


extern void wakeme_after_rcu(struct rcu_head  *head);



/**

 * synchronize_sched - block until all CPUs have exited any non-preemptive

 * kernel code sequences.

 *

 * 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.

 */

#define synchronize_sched() __synchronize_sched()



/**

 * call_rcu - Queue an RCU callback for invocation after a grace period.

 * @head: structure to be used for queueing the RCU updates.

include/linux/rcutree.h

+2 −2
Original line number Diff line number Diff line
@@ -53,6 +53,8 @@ static inline void __rcu_read_unlock(void) 
	preempt_enable();

}



#define __synchronize_sched() synchronize_rcu()



static inline void exit_rcu(void)

{

}
@@ -68,8 +70,6 @@ static inline void __rcu_read_unlock_bh(void) 
	local_bh_enable();

}



#define __synchronize_sched() synchronize_rcu()



extern void call_rcu_sched(struct rcu_head *head,

			   void (*func)(struct rcu_head *rcu));

kernel/rcupdate.c

+43 −1
Original line number Diff line number Diff line
@@ -74,6 +74,8 @@ void wakeme_after_rcu(struct rcu_head *head) 
	complete(&rcu->completion);

}



#ifdef CONFIG_TREE_PREEMPT_RCU



/**

 * synchronize_rcu - wait until a grace period has elapsed.

 *
@@ -87,7 +89,7 @@ void synchronize_rcu(void) 
{

	struct rcu_synchronize rcu;



	if (rcu_blocking_is_gp())

	if (!rcu_scheduler_active)

		return;



	init_completion(&rcu.completion);
@@ -98,6 +100,46 @@ void synchronize_rcu(void) 
}

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.

 *