From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [OOPS] 2.6.11 - NMI lockup with CFQ scheduler Date: Thu, 07 Apr 2005 09:39:43 -0400 Message-ID: <1112881183.5842.13.camel@mulgrave> References: <20050329120311.GO16636@suse.de> <1112804840.5476.16.camel@mulgrave> <20050406175838.GC15165@suse.de> <1112811607.5555.15.camel@mulgrave> <20050406190838.GE15165@suse.de> <1112821799.5850.19.camel@mulgrave> <20050407064934.GJ15165@suse.de> <1112879919.5842.3.camel@mulgrave> <20050407132205.GA16517@infradead.org> <1112880658.5842.10.camel@mulgrave> <20050407133222.GJ1847@suse.de> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from stat16.steeleye.com ([209.192.50.48]:3238 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S262477AbVDGNjt (ORCPT ); Thu, 7 Apr 2005 09:39:49 -0400 In-Reply-To: <20050407133222.GJ1847@suse.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Jens Axboe Cc: Christoph Hellwig , Chris Rankin , Linux Kernel , SCSI Mailing List On Thu, 2005-04-07 at 15:32 +0200, Jens Axboe wrote: > I think Christophs point is that why add sdev_lock as a pointer, instead > of just killing it? It's only used in one location, so it's not really > that confusing (and a comment could fix that). Because any use of sdev->request_queue->queue_lock would likely succeed even after we've freed the device and released the queue. If it's a pointer and we null it after free and release, then any later use will trigger an immediate NULL deref oops. Since we've had so many nasty problems around refcounting, I just would like to assure myself that we're doing everything correctly (I really believe we are, but empirical evidence is also nice). James