Date: Tue, 6 Sep 2016 17:16:59 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r305482 - head/sys/kern Message-ID: <201609061716.u86HGxvm037385@repo.freebsd.org>
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Author: mjg Date: Tue Sep 6 17:16:59 2016 New Revision: 305482 URL: https://svnweb.freebsd.org/changeset/base/305482 Log: 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 Reviewed by: jhb MFC after: 1 week Modified: head/sys/kern/kern_condvar.c Modified: head/sys/kern/kern_condvar.c ============================================================================== --- head/sys/kern/kern_condvar.c Tue Sep 6 17:08:31 2016 (r305481) +++ head/sys/kern/kern_condvar.c Tue Sep 6 17:16:59 2016 (r305482) @@ -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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