From owner-freebsd-threads@FreeBSD.ORG Thu Jul 18 15:09:07 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 31C215B2 for ; Thu, 18 Jul 2013 15:09:07 +0000 (UTC) (envelope-from deischen@freebsd.org) Received: from mail.netplex.net (mail.netplex.net [204.213.176.9]) by mx1.freebsd.org (Postfix) with ESMTP id EC2A435E for ; Thu, 18 Jul 2013 15:09:06 +0000 (UTC) Received: from sea.ntplx.net (sea.ntplx.net [204.213.176.11]) by mail.netplex.net (8.14.6/8.14.6/NETPLEX) with ESMTP id r6IF94vQ001389; Thu, 18 Jul 2013 11:09:05 -0400 X-Virus-Scanned: by AMaViS and Clam AntiVirus (mail.netplex.net) X-Greylist: Message whitelisted by DRAC access database, not delayed by milter-greylist-4.4.1 (mail.netplex.net [204.213.176.9]); Thu, 18 Jul 2013 11:09:05 -0400 (EDT) Date: Thu, 18 Jul 2013 11:09:04 -0400 (EDT) From: Daniel Eischen X-X-Sender: eischen@sea.ntplx.net To: Joe Marcus Clarke Subject: Re: Mutexes and error checking In-Reply-To: <51E71D4F.5030502@marcuscom.com> Message-ID: References: <51E71D4F.5030502@marcuscom.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: Koop Mast , freebsd-threads@freebsd.org X-BeenThere: freebsd-threads@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list Reply-To: Daniel Eischen List-Id: Threading on FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 18 Jul 2013 15:09:07 -0000 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. -- DE