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Commit 0cd397d3 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
Browse files

rcu: Add synchronize_srcu_expedited() 



This patch creates a synchronize_srcu_expedited() that uses
synchronize_sched_expedited() where synchronize_srcu()
uses synchronize_sched().  The synchronize_srcu() and
synchronize_srcu_expedited() functions become one-liners that
pass synchronize_sched() or synchronize_sched_expedited(),
repectively, to a new __synchronize_srcu() function.

While in the file, move the EXPORT_SYMBOL_GPL()s to immediately
follow the corresponding functions.

Requested-by: default avatarAvi Kivity <avi@redhat.com>
Tested-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: default avatarJosh Triplett <josh@joshtriplett.org>
Reviewed-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: avi@redhat.com
LKML-Reference: <12565226354038-git-send-email->
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 9b1d82fa

include/linux/srcu.h

+1 −0
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ void cleanup_srcu_struct(struct srcu_struct *sp); 
int srcu_read_lock(struct srcu_struct *sp) __acquires(sp);

void srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);

void synchronize_srcu(struct srcu_struct *sp);

void synchronize_srcu_expedited(struct srcu_struct *sp);

long srcu_batches_completed(struct srcu_struct *sp);



#endif

kernel/srcu.c

+51 −23
Original line number Diff line number Diff line
@@ -49,6 +49,7 @@ int init_srcu_struct(struct srcu_struct *sp) 
	sp->per_cpu_ref = alloc_percpu(struct srcu_struct_array);

	return (sp->per_cpu_ref ? 0 : -ENOMEM);

}

EXPORT_SYMBOL_GPL(init_srcu_struct);



/*

 * srcu_readers_active_idx -- returns approximate number of readers
@@ -97,6 +98,7 @@ void cleanup_srcu_struct(struct srcu_struct *sp) 
	free_percpu(sp->per_cpu_ref);

	sp->per_cpu_ref = NULL;

}

EXPORT_SYMBOL_GPL(cleanup_srcu_struct);



/**

 * srcu_read_lock - register a new reader for an SRCU-protected structure.
@@ -118,6 +120,7 @@ int srcu_read_lock(struct srcu_struct *sp) 
	preempt_enable();

	return idx;

}

EXPORT_SYMBOL_GPL(srcu_read_lock);



/**

 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
@@ -136,22 +139,12 @@ void srcu_read_unlock(struct srcu_struct *sp, int idx) 
	per_cpu_ptr(sp->per_cpu_ref, smp_processor_id())->c[idx]--;

	preempt_enable();

}

EXPORT_SYMBOL_GPL(srcu_read_unlock);



/**

 * synchronize_srcu - wait for prior SRCU read-side critical-section completion

 * @sp: srcu_struct with which to synchronize.

 *

 * Flip the completed counter, and wait for the old count to drain to zero.

 * As with classic RCU, the updater must use some separate means of

 * synchronizing concurrent updates.  Can block; must be called from

 * process context.

 *

 * Note that it is illegal to call synchornize_srcu() from the corresponding

 * SRCU read-side critical section; doing so will result in deadlock.

 * However, it is perfectly legal to call synchronize_srcu() on one

 * srcu_struct from some other srcu_struct's read-side critical section.

/*

 * Helper function for synchronize_srcu() and synchronize_srcu_expedited().

 */

void synchronize_srcu(struct srcu_struct *sp)

void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))

{

	int idx;
@@ -173,7 +166,7 @@ void synchronize_srcu(struct srcu_struct *sp) 
		return;

	}



	synchronize_sched();  /* Force memory barrier on all CPUs. */

	sync_func();  /* Force memory barrier on all CPUs. */



	/*

	 * The preceding synchronize_sched() ensures that any CPU that
@@ -190,7 +183,7 @@ void synchronize_srcu(struct srcu_struct *sp) 
	idx = sp->completed & 0x1;

	sp->completed++;



	synchronize_sched();  /* Force memory barrier on all CPUs. */

	sync_func();  /* Force memory barrier on all CPUs. */



	/*

	 * At this point, because of the preceding synchronize_sched(),
@@ -203,7 +196,7 @@ void synchronize_srcu(struct srcu_struct *sp) 
	while (srcu_readers_active_idx(sp, idx))

		schedule_timeout_interruptible(1);



	synchronize_sched();  /* Force memory barrier on all CPUs. */

	sync_func();  /* Force memory barrier on all CPUs. */



	/*

	 * The preceding synchronize_sched() forces all srcu_read_unlock()
@@ -236,6 +229,47 @@ void synchronize_srcu(struct srcu_struct *sp) 
	mutex_unlock(&sp->mutex);

}



/**

 * synchronize_srcu - wait for prior SRCU read-side critical-section completion

 * @sp: srcu_struct with which to synchronize.

 *

 * Flip the completed counter, and wait for the old count to drain to zero.

 * As with classic RCU, the updater must use some separate means of

 * synchronizing concurrent updates.  Can block; must be called from

 * process context.

 *

 * Note that it is illegal to call synchronize_srcu() from the corresponding

 * SRCU read-side critical section; doing so will result in deadlock.

 * However, it is perfectly legal to call synchronize_srcu() on one

 * srcu_struct from some other srcu_struct's read-side critical section.

 */

void synchronize_srcu(struct srcu_struct *sp)

{

	__synchronize_srcu(sp, synchronize_sched);

}

EXPORT_SYMBOL_GPL(synchronize_srcu);



/**

 * synchronize_srcu_expedited - like synchronize_srcu, but less patient

 * @sp: srcu_struct with which to synchronize.

 *

 * Flip the completed counter, and wait for the old count to drain to zero.

 * As with classic RCU, the updater must use some separate means of

 * synchronizing concurrent updates.  Can block; must be called from

 * process context.

 *

 * Note that it is illegal to call synchronize_srcu_expedited()

 * from the corresponding SRCU read-side critical section; doing so

 * will result in deadlock.  However, it is perfectly legal to call

 * synchronize_srcu_expedited() on one srcu_struct from some other

 * srcu_struct's read-side critical section.

 */

void synchronize_srcu_expedited(struct srcu_struct *sp)

{

	__synchronize_srcu(sp, synchronize_sched_expedited);

}

EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);



/**

 * srcu_batches_completed - return batches completed.

 * @sp: srcu_struct on which to report batch completion.
@@ -248,10 +282,4 @@ long srcu_batches_completed(struct srcu_struct *sp) 
{

	return sp->completed;

}



EXPORT_SYMBOL_GPL(init_srcu_struct);

EXPORT_SYMBOL_GPL(cleanup_srcu_struct);

EXPORT_SYMBOL_GPL(srcu_read_lock);

EXPORT_SYMBOL_GPL(srcu_read_unlock);

EXPORT_SYMBOL_GPL(synchronize_srcu);

EXPORT_SYMBOL_GPL(srcu_batches_completed);