From owner-freebsd-threads@FreeBSD.ORG Thu Jul 18 15:13:36 2013 Return-Path: Delivered-To: freebsd-threads@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id 7C198616 for ; Thu, 18 Jul 2013 15:13:36 +0000 (UTC) (envelope-from marcus@marcuscom.com) Received: from av-tac-rtp.cisco.com (av-tac-rtp.cisco.com [64.102.19.209]) by mx1.freebsd.org (Postfix) with ESMTP id 1C76E37E for ; Thu, 18 Jul 2013 15:13:35 +0000 (UTC) X-TACSUNS: Virus Scanned Received: from chook.cisco.com (localhost.cisco.com [127.0.0.1]) by av-tac-rtp.cisco.com (8.13.8+Sun/8.13.8) with ESMTP id r6IFDYnB010665 for ; Thu, 18 Jul 2013 11:13:34 -0400 (EDT) Received: from dhcp-10-150-54-149.cisco.com (dhcp-10-150-54-149.cisco.com [10.150.54.149]) by chook.cisco.com (8.13.8+Sun/8.13.8) with ESMTP id r6IFDVBW008377; Thu, 18 Jul 2013 11:13:31 -0400 (EDT) Message-ID: <51E8061B.60906@marcuscom.com> Date: Thu, 18 Jul 2013 11:13:31 -0400 From: Joe Marcus Clarke User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20130620 Thunderbird/17.0.7 MIME-Version: 1.0 To: Daniel Eischen Subject: Re: Mutexes and error checking References: <51E71D4F.5030502@marcuscom.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Koop Mast , freebsd-threads@freebsd.org X-BeenThere: freebsd-threads@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Threading on FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 18 Jul 2013 15:13:36 -0000 On 7/18/13 11:09 AM, Daniel Eischen wrote: > On Wed, 17 Jul 2013, Joe Marcus Clarke wrote: > >> It seems we might have a discrepancy between the way our pthread >> implementation works compared to Linux. If a mutex is set to NORMAL >> type and one goes to unlock it, EPERM is returned unless the current >> thread is the mutex owner. While this sounds perfectly sane, it appears >> Linux only returns EPERM if the mutex type is ERRORCHECK. >> >> We are seeing some problems in ported code because of this. As a >> suggestion, if people agree, would it be possible to emulate the >> behavior of Linux and only return EPERM if the mutex is of type >> ERRORCHECK or RECURSVIE? > > First, any software that does that is broken. > > Second, the POSIX spec seems to imply that an error is returned > when a different thread tries to unlock an already locked mutex: > > > http://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_mutex_lock.htm > > > Is the mutex robust or not robust? If not robust > (PTHREAD_MUTEX_STALLED), then a PTHREAD_MUTEX_NORMAL mutex > cannot be unlocked by any other thread than the owner. > So, it would seem to be wrong to _not_ return an > error when the mutex is not unlocked after > pthread_mutex_unlock() returns. > Don't get me wrong, I agree with you. This behavior should result in EPERM. However, my comment was more on the portability side to maintain parity with Linux in order to support the 3rd party code people wanting to run on FreeBSD. We can workaround it in some cases, but I was floating up to you guys to perhaps create a broader workaround. Joe -- PGP Key : http://www.marcuscom.com/pgp.asc