From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: Re: [PATCH] QStor SATA/RAID driver for 2.6.9-rc3 Date: Tue, 12 Oct 2004 12:59:01 -0400 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <416C0D55.1020603@rtr.ca> References: <4161A06D.8010601@rtr.ca> <416547B6.5080505@rtr.ca> <20041007150709.B12688@i nfradead.org> <4165624C.5060405@rtr.ca> <416565DB.4050006@pobox.com> <4165A4 5D.2090200@rtr.ca> <4165A766.1040104@pobox.com> <4165A85D.7080704@rtr.ca> <4 165AB1B.8000204@pobox.com> <4165ACF8.8060208@rtr.ca> <20041007221537.A17712@infradead.org> <1097241583.2412.15.camel@mulgrave> <4166AF2F.6070904@rtr.ca> <1097249266.1678.40.camel@mulgrave> <4166B48E.3020006@rtr.ca> <1097250465.2412.49.camel@mulgrave> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from cpu1185.adsl.bellglobal.com ([207.236.110.166]:28099 "EHLO mail.rtr.ca") by vger.kernel.org with ESMTP id S266274AbUJLRAv (ORCPT ); Tue, 12 Oct 2004 13:00:51 -0400 In-Reply-To: <1097250465.2412.49.camel@mulgrave> List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: Christoph Hellwig , Jeff Garzik , Mark Lord , Linux Kernel , SCSI Mailing List James Bottomley wrote: > On Fri, 2004-10-08 at 10:38, Mark Lord wrote: > >>Can deadlock occur here, since qstor.c is already using schedule_work() >>as part of it's internal bottom-half handling for abnormal conditions? >> >>Eg. hotplug event -> schedule_work -> mid-layer -> queuecommand >> --> sleep :: interrupt -> schedule_work -> deadlock? >> > > > Since you wouldn't go straight from schedule_work->mid-layer, I assume > you mean that when the workqueue thread runs the work? Yes. The workqueue thread will invoke the mid-layer function, which will do a queuecommand, which will return to the mid-layer, which will then SLEEP waiting for the command to complete, which will sleep that workqueue thread. As part of the interrupt processing to complete the command in the LLD, it is possible that schedule_work may be necessary, requiring that a workqueue thread be run. If this means the same thread that is already sleeping courtesy of the mid-layer, then we could have a problem. Comments? -- Mark Lord (hdparm keeper & the original "Linux IDE Guy")