From owner-cvs-all@FreeBSD.ORG  Fri Jul  9 17:46:27 2004
Return-Path: <owner-cvs-all@FreeBSD.ORG>
Delivered-To: cvs-all@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id D49F016A4CE; Fri,  9 Jul 2004 17:46:27 +0000 (GMT)
Received: from repoman.freebsd.org (repoman.freebsd.org [216.136.204.115])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id B71E743D3F; Fri,  9 Jul 2004 17:46:27 +0000 (GMT)
	(envelope-from jhb@FreeBSD.org)
Received: from repoman.freebsd.org (localhost [127.0.0.1])
	by repoman.freebsd.org (8.12.11/8.12.11) with ESMTP id i69HkRcc087028;
	Fri, 9 Jul 2004 17:46:27 GMT
	(envelope-from jhb@repoman.freebsd.org)
Received: (from jhb@localhost)
	by repoman.freebsd.org (8.12.11/8.12.11/Submit) id i69HkRJS087027;
	Fri, 9 Jul 2004 17:46:27 GMT
	(envelope-from jhb)
Message-Id: <200407091746.i69HkRJS087027@repoman.freebsd.org>
From: John Baldwin <jhb@FreeBSD.org>
Date: Fri, 9 Jul 2004 17:46:27 +0000 (UTC)
To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org,
	cvs-all@FreeBSD.org
X-FreeBSD-CVS-Branch: HEAD
Subject: cvs commit: src/sys/kern subr_witness.c
X-BeenThere: cvs-all@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: CVS commit messages for the entire tree <cvs-all.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-all>,
	<mailto:cvs-all-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/cvs-all>
List-Post: <mailto:cvs-all@freebsd.org>
List-Help: <mailto:cvs-all-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-all>,
	<mailto:cvs-all-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 09 Jul 2004 17:46:28 -0000

jhb         2004-07-09 17:46:27 UTC

  FreeBSD src repository

  Modified files:
    sys/kern             subr_witness.c 
  Log:
  Check the lock lists to see if they are empty directly rather than
  assigning a pointer to the list and then dereferencing the pointer as a
  second step.  When the first spin lock is acquired, curthread is not in
  a critical section so it may be preempted and would end up using another
  CPUs lock list instead of its own.
  
  When this code was in witness_lock() this sequence was safe as curthread
  was in a critical section already since witness_lock() is called after the
  lock is acquired.
  
  Tested by:      Daniel Lang dl at leo.org
  
  Revision  Changes    Path
  1.175     +21 -9     src/sys/kern/subr_witness.c