Commit 6859d1f2 authored by NeilBrown's avatar NeilBrown Committed by Chuck Lever
Browse files

SUNRPC: make rqst_should_sleep() idempotent() 



Based on its name you would think that rqst_should_sleep() would be
read-only, not changing anything.  But in fact it will clear
SP_TASK_PENDING if that was set.  This is surprising, and it blurs the
line between "check for work to do" and "dequeue work to do".

So change the "test_and_clear" to simple "test" and clear the bit once
the thread has decided to wake up and return to the caller.

With this, it makes sense to *always* set SP_TASK_PENDING when asked,
rather than to set it only if no thread could be woken up.

[ cel: Previously TASK_PENDING indicated there is work waiting but no
idle threads were found to pick up that work. After this patch, it acts
as an XPT_BUSY flag for wake-ups that have no associated xprt. ]

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent d2f0ef1c

net/sunrpc/svc_xprt.c

+5 −3
Original line number Diff line number Diff line
@@ -581,8 +581,8 @@ void svc_wake_up(struct svc_serv *serv) 
{

	struct svc_pool *pool = &serv->sv_pools[0];



	if (!svc_pool_wake_idle_thread(pool))

	set_bit(SP_TASK_PENDING, &pool->sp_flags);

	svc_pool_wake_idle_thread(pool);

}

EXPORT_SYMBOL_GPL(svc_wake_up);
@@ -704,7 +704,7 @@ rqst_should_sleep(struct svc_rqst *rqstp) 
	struct svc_pool		*pool = rqstp->rq_pool;



	/* did someone call svc_wake_up? */

	if (test_and_clear_bit(SP_TASK_PENDING, &pool->sp_flags))

	if (test_bit(SP_TASK_PENDING, &pool->sp_flags))

		return false;



	/* was a socket queued? */
@@ -748,6 +748,7 @@ static struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp) 


	set_bit(RQ_BUSY, &rqstp->rq_flags);

	smp_mb__after_atomic();

	clear_bit(SP_TASK_PENDING, &pool->sp_flags);

	rqstp->rq_xprt = svc_xprt_dequeue(pool);

	if (rqstp->rq_xprt)

		goto out_found;
@@ -756,6 +757,7 @@ static struct svc_xprt *svc_get_next_xprt(struct svc_rqst *rqstp) 
		return NULL;

	return NULL;

out_found:

	clear_bit(SP_TASK_PENDING, &pool->sp_flags);

	/* Normally we will wait up to 5 seconds for any required

	 * cache information to be provided.

	 */