Author: mjg
Date: Sat Dec 31 12:39:34 2016
New Revision: 310962
URL: https://svnweb.freebsd.org/changeset/base/310962
Log:
MFC r305482:
cv: do a lockless check for no waiters in cv_signal and cv_broadcastpri
In case of some consumers like zfs there are no waiters vast majority of
the time
Modified:
stable/11/sys/kern/kern_condvar.c
Directory Properties:
stable/11/ (props changed)
Modified: stable/11/sys/kern/kern_condvar.c
==============================================================================
--- stable/11/sys/kern/kern_condvar.c Sat Dec 31 12:39:15 2016
(r310961)
+++ stable/11/sys/kern/kern_condvar.c Sat Dec 31 12:39:34 2016
(r310962)
@@ -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.
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