Date: Sat, 31 Dec 2016 12:39:35 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r310962 - stable/11/sys/kern Message-ID: <201612311239.uBVCdZ1s080206@repo.freebsd.org>
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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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