From owner-svn-src-stable-11@freebsd.org  Sat Dec 31 12:39:36 2016
Return-Path: <owner-svn-src-stable-11@freebsd.org>
Delivered-To: svn-src-stable-11@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id 39D02C981AC;
 Sat, 31 Dec 2016 12:39:36 +0000 (UTC) (envelope-from mjg@FreeBSD.org)
Received: from repo.freebsd.org (repo.freebsd.org
 [IPv6:2610:1c1:1:6068::e6a:0])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id 0982E12B0;
 Sat, 31 Dec 2016 12:39:35 +0000 (UTC) (envelope-from mjg@FreeBSD.org)
Received: from repo.freebsd.org ([127.0.1.37])
 by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id uBVCdZl7080207;
 Sat, 31 Dec 2016 12:39:35 GMT (envelope-from mjg@FreeBSD.org)
Received: (from mjg@localhost)
 by repo.freebsd.org (8.15.2/8.15.2/Submit) id uBVCdZ1s080206;
 Sat, 31 Dec 2016 12:39:35 GMT (envelope-from mjg@FreeBSD.org)
Message-Id: <201612311239.uBVCdZ1s080206@repo.freebsd.org>
X-Authentication-Warning: repo.freebsd.org: mjg set sender to mjg@FreeBSD.org
 using -f
From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Sat, 31 Dec 2016 12:39:35 +0000 (UTC)
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
X-SVN-Group: stable-11
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
X-BeenThere: svn-src-stable-11@freebsd.org
X-Mailman-Version: 2.1.23
Precedence: list
List-Id: SVN commit messages for only the 11-stable src tree
 <svn-src-stable-11.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/svn-src-stable-11>, 
 <mailto:svn-src-stable-11-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-stable-11/>
List-Post: <mailto:svn-src-stable-11@freebsd.org>
List-Help: <mailto:svn-src-stable-11-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/svn-src-stable-11>, 
 <mailto:svn-src-stable-11-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 31 Dec 2016 12:39:36 -0000

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.