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SUNRPC: make rqst_should_sleep() idempotent()

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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: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
NeilBrown 2023-07-31 16:48:28 +10:00 committed by Chuck Lever
parent d2f0ef1cbf
commit 6859d1f290
1 changed files with 5 additions and 3 deletions
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8
net/sunrpc/svc_xprt.c
View file

@ -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);
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.
*/