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Commit 2c42818e authored by Paul E. McKenney's avatar Paul E. McKenney
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rcu: Abstract common code for RCU grace-period-wait primitives 



Pull the code that waits for an RCU grace period into a single function,
which is then called by synchronize_rcu() and friends in the case of
TREE_RCU and TREE_PREEMPT_RCU, and from rcu_barrier() and friends in
the case of TINY_RCU and TINY_PREEMPT_RCU.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent f039d1f1

include/linux/rcupdate.h

+73 −57
Original line number Diff line number Diff line
@@ -66,11 +66,73 @@ static inline void rcutorture_record_progress(unsigned long vernum) 
#define ULONG_CMP_LT(a, b)	(ULONG_MAX / 2 < (a) - (b))



/* Exported common interfaces */



#ifdef CONFIG_PREEMPT_RCU



/**

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

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

 * @func: actual callback function to be invoked after the grace period

 *

 * The callback function will be invoked some time after a full grace

 * period elapses, in other words after all pre-existing RCU read-side

 * critical sections have completed.  However, the callback function

 * might well execute concurrently with RCU read-side critical sections

 * that started after call_rcu() was invoked.  RCU read-side critical

 * sections are delimited by rcu_read_lock() and rcu_read_unlock(),

 * and may be nested.

 */

extern void call_rcu(struct rcu_head *head,

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



#else /* #ifdef CONFIG_PREEMPT_RCU */



/* In classic RCU, call_rcu() is just call_rcu_sched(). */

#define	call_rcu	call_rcu_sched



#endif /* #else #ifdef CONFIG_PREEMPT_RCU */



/**

 * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period.

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

 * @func: actual callback function to be invoked after the grace period

 *

 * The callback function will be invoked some time after a full grace

 * period elapses, in other words after all currently executing RCU

 * read-side critical sections have completed. call_rcu_bh() assumes

 * that the read-side critical sections end on completion of a softirq

 * handler. This means that read-side critical sections in process

 * context must not be interrupted by softirqs. This interface is to be

 * used when most of the read-side critical sections are in softirq context.

 * RCU read-side critical sections are delimited by :

 *  - rcu_read_lock() and  rcu_read_unlock(), if in interrupt context.

 *  OR

 *  - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context.

 *  These may be nested.

 */

extern void call_rcu_bh(struct rcu_head *head,

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



/**

 * call_rcu_sched() - Queue an RCU for invocation after sched grace period.

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

 * @func: actual callback function to be invoked after the grace period

 *

 * The callback function will be invoked some time after a full grace

 * period elapses, in other words after all currently executing RCU

 * read-side critical sections have completed. call_rcu_sched() assumes

 * that the read-side critical sections end on enabling of preemption

 * or on voluntary preemption.

 * RCU read-side critical sections are delimited by :

 *  - rcu_read_lock_sched() and  rcu_read_unlock_sched(),

 *  OR

 *  anything that disables preemption.

 *  These may be nested.

 */

extern void call_rcu_sched(struct rcu_head *head,

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



extern void synchronize_sched(void);

extern void rcu_barrier_bh(void);

extern void rcu_barrier_sched(void);



static inline void __rcu_read_lock_bh(void)

{
@@ -143,6 +205,15 @@ static inline void rcu_exit_nohz(void) 


#endif /* #else #ifdef CONFIG_NO_HZ */



/*

 * Infrastructure to implement the synchronize_() primitives in

 * TREE_RCU and rcu_barrier_() primitives in TINY_RCU.

 */



typedef void call_rcu_func_t(struct rcu_head *head,

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

void wait_rcu_gp(call_rcu_func_t crf);



#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)

#include <linux/rcutree.h>

#elif defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU)
@@ -723,61 +794,6 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) 
#define RCU_INIT_POINTER(p, v) \

		p = (typeof(*v) __force __rcu *)(v)



/* Infrastructure to implement the synchronize_() primitives. */



struct rcu_synchronize {

	struct rcu_head head;

	struct completion completion;

};



extern void wakeme_after_rcu(struct rcu_head  *head);



#ifdef CONFIG_PREEMPT_RCU



/**

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

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

 * @func: actual callback function to be invoked after the grace period

 *

 * The callback function will be invoked some time after a full grace

 * period elapses, in other words after all pre-existing RCU read-side

 * critical sections have completed.  However, the callback function

 * might well execute concurrently with RCU read-side critical sections

 * that started after call_rcu() was invoked.  RCU read-side critical

 * sections are delimited by rcu_read_lock() and rcu_read_unlock(),

 * and may be nested.

 */

extern void call_rcu(struct rcu_head *head,

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



#else /* #ifdef CONFIG_PREEMPT_RCU */



/* In classic RCU, call_rcu() is just call_rcu_sched(). */

#define	call_rcu	call_rcu_sched



#endif /* #else #ifdef CONFIG_PREEMPT_RCU */



/**

 * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period.

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

 * @func: actual callback function to be invoked after the grace period

 *

 * The callback function will be invoked some time after a full grace

 * period elapses, in other words after all currently executing RCU

 * read-side critical sections have completed. call_rcu_bh() assumes

 * that the read-side critical sections end on completion of a softirq

 * handler. This means that read-side critical sections in process

 * context must not be interrupted by softirqs. This interface is to be

 * used when most of the read-side critical sections are in softirq context.

 * RCU read-side critical sections are delimited by :

 *  - rcu_read_lock() and  rcu_read_unlock(), if in interrupt context.

 *  OR

 *  - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context.

 *  These may be nested.

 */

extern void call_rcu_bh(struct rcu_head *head,

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



/*

 * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally

 * by call_rcu() and rcu callback execution, and are therefore not part of the

include/linux/rcutiny.h

+15 −1
Original line number Diff line number Diff line
@@ -31,6 +31,16 @@ static inline void rcu_init(void) 
{

}



static inline void rcu_barrier_bh(void)

{

	wait_rcu_gp(call_rcu_bh);

}



static inline void rcu_barrier_sched(void)

{

	wait_rcu_gp(call_rcu_sched);

}



#ifdef CONFIG_TINY_RCU



static inline void synchronize_rcu_expedited(void)
@@ -45,9 +55,13 @@ static inline void rcu_barrier(void) 


#else /* #ifdef CONFIG_TINY_RCU */



void rcu_barrier(void);

void synchronize_rcu_expedited(void);



static inline void rcu_barrier(void)

{

	wait_rcu_gp(call_rcu);

}



#endif /* #else #ifdef CONFIG_TINY_RCU */



static inline void synchronize_rcu_bh(void)

include/linux/rcutree.h

+2 −0
Original line number Diff line number Diff line
@@ -67,6 +67,8 @@ static inline void synchronize_rcu_bh_expedited(void) 
}



extern void rcu_barrier(void);

extern void rcu_barrier_bh(void);

extern void rcu_barrier_sched(void);



extern unsigned long rcutorture_testseq;

extern unsigned long rcutorture_vernum;

kernel/rcupdate.c

+20 −1
Original line number Diff line number Diff line
@@ -94,11 +94,16 @@ EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); 


#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */



struct rcu_synchronize {

	struct rcu_head head;

	struct completion completion;

};



/*

 * Awaken the corresponding synchronize_rcu() instance now that a

 * grace period has elapsed.

 */

void wakeme_after_rcu(struct rcu_head  *head)

static void wakeme_after_rcu(struct rcu_head  *head)

{

	struct rcu_synchronize *rcu;
@@ -106,6 +111,20 @@ void wakeme_after_rcu(struct rcu_head *head) 
	complete(&rcu->completion);

}



void wait_rcu_gp(call_rcu_func_t crf)

{

	struct rcu_synchronize rcu;



	init_rcu_head_on_stack(&rcu.head);

	init_completion(&rcu.completion);

	/* Will wake me after RCU finished. */

	crf(&rcu.head, wakeme_after_rcu);

	/* Wait for it. */

	wait_for_completion(&rcu.completion);

	destroy_rcu_head_on_stack(&rcu.head);

}

EXPORT_SYMBOL_GPL(wait_rcu_gp);



#ifdef CONFIG_PROVE_RCU

/*

 * wrapper function to avoid #include problems.

kernel/rcutiny.c

+0 −28
Original line number Diff line number Diff line
@@ -281,34 +281,6 @@ void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) 
}

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.

 */