From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932251AbWI0OE5 (ORCPT ); Wed, 27 Sep 2006 10:04:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932259AbWI0OE5 (ORCPT ); Wed, 27 Sep 2006 10:04:57 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:4769 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S932251AbWI0OE4 (ORCPT ); Wed, 27 Sep 2006 10:04:56 -0400 Date: Wed, 27 Sep 2006 15:57:05 +0200 From: Ingo Molnar To: Srinivasa Ds Cc: dm-devel@redhat.com, linux-lvm@redhat.com, linux-kernel@vger.kernel.org, agk@redhat.com Subject: Re: [RFC] Reverting "bd_mount_mutex" to "bd_mount_sem" Message-ID: <20060927135705.GA30311@elte.hu> References: <451A78DF.1060901@in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <451A78DF.1060901@in.ibm.com> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: -2.9 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.9 required=5.9 tests=ALL_TRUSTED,AWL,BAYES_50 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts 0.5 BAYES_50 BODY: Bayesian spam probability is 40 to 60% [score: 0.5000] -0.1 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Srinivasa Ds wrote: > On debugging I found out that,"dmsetup suspend " calls > "freeze_bdev()",which locks "bd_mount_mutex" to make sure that no new > mounts happen on bdev until thaw_bdev() is called. > This "thaw_bdev()" is getting called when we resume the device > through "dmsetup resume ". > Hence we have 2 processes,one of which locks > "bd_mount_mutex"(dmsetup suspend) and Another(dmsetup resume) unlocks > it. hm, to me this seems quite a fragile construct - even if the mutex-debugging warning is worked around by reverting to a semaphore. Ingo