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cv: do a lockless check for no waiters in cv_signal and cv_broadcastpri

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In case of some consumers like zfs there are no waiters vast majority of
the time

Reviewed by:	jhb
MFC after:	1 week
This commit is contained in:
Mateusz Guzik 2016-09-06 17:16:59 +00:00
parent 949b56ba66
commit 5b7d9ae2fd
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=305482
1 changed files with 4 additions and 0 deletions
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4
sys/kern/kern_condvar.c
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@ -397,6 +397,8 @@ cv_signal(struct cv *cvp)
{
int wakeup_swapper;
if (cvp->cv_waiters == 0)
return;
wakeup_swapper = 0;
sleepq_lock(cvp);
if (cvp->cv_waiters > 0) {
@ -424,6 +426,8 @@ cv_broadcastpri(struct cv *cvp, int pri)
{
int wakeup_swapper;
if (cvp->cv_waiters == 0)
return;
/*
* XXX sleepq_broadcast pri argument changed from -1 meaning
* no pri to 0 meaning no pri.