From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761214AbXK1PAz (ORCPT ); Wed, 28 Nov 2007 10:00:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752679AbXK1PAs (ORCPT ); Wed, 28 Nov 2007 10:00:48 -0500 Received: from mx1.riseup.net ([204.13.164.18]:37764 "EHLO mx1.riseup.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751175AbXK1PAr (ORCPT ); Wed, 28 Nov 2007 10:00:47 -0500 Date: Wed, 28 Nov 2007 16:00:55 +0100 From: Matthias Kaehlcke To: Larry Finger Cc: LKML Subject: Re: Question regarding mutex locking Message-ID: <20071128150055.GK20238@traven> Mail-Followup-To: Matthias Kaehlcke , Larry Finger , LKML References: <474CF06C.8020208@lwfinger.net> <20071128081031.GF20238@traven> <474D7F5B.9090008@lwfinger.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <474D7F5B.9090008@lwfinger.net> User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org El Wed, Nov 28, 2007 at 08:46:51AM -0600 Larry Finger ha dit: > Matthias Kaehlcke wrote: > > El Tue, Nov 27, 2007 at 10:37:00PM -0600 Larry Finger ha dit: > > > >> If a particular routine needs to lock a mutex, but it may be entered with that mutex already locked, > >> would the following code be SMP safe? > >> > >> hold_lock = mutex_trylock() > >> > >> ... > >> > >> if (hold_lock) > >> mutex_unlock() > > > > this is wont work, a mutex must not be released from another > > context than the one that acquired it. > > I thought that mutex_trylock() returned 1 if it got the lock and 0 if not. If that is true, wouldn't > the if statement only unlock if the lock was obtained in this routine? you're right, sorry i read to fast and interpreted that you want to release the mutex in any case -- Matthias Kaehlcke Linux Application Developer Barcelona You must have a plan. If you don't have a plan, you'll become part of somebody else's plan .''`. using free software / Debian GNU/Linux | http://debian.org : :' : `. `'` gpg --keyserver pgp.mit.edu --recv-keys 47D8E5D4 `-