From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752644AbbH1Gko (ORCPT ); Fri, 28 Aug 2015 02:40:44 -0400 Received: from mx2.suse.de ([195.135.220.15]:41010 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751525AbbH1Gkl (ORCPT ); Fri, 28 Aug 2015 02:40:41 -0400 Message-ID: <55E00266.8030809@suse.de> Date: Fri, 28 Aug 2015 08:40:38 +0200 From: Hannes Reinecke User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: mhocko@kernel.org, "James E.J. Bottomley" CC: Dan Williams , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Michal Hocko Subject: Re: [PATCH] scsi: fix scsi_error_handler vs. scsi_host_dev_release race References: <1440699420-30499-1-git-send-email-mhocko@kernel.org> In-Reply-To: <1440699420-30499-1-git-send-email-mhocko@kernel.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/27/2015 08:16 PM, mhocko@kernel.org wrote: > From: Michal Hocko > > b9d5c6b7ef57 ("[SCSI] cleanup setting task state in > scsi_error_handler()") has introduced a race between scsi_error_handler > and scsi_host_dev_release resulting in the hang when the device goes > away because scsi_error_handler might miss a wake up: > > CPU0 CPU1 > scsi_error_handler scsi_host_dev_release > kthread_stop() > kthread_should_stop() > test_bit(KTHREAD_SHOULD_STOP) > set_bit(KTHREAD_SHOULD_STOP) > wake_up_process() > wait_for_completion() > > set_current_state(TASK_INTERRUPTIBLE) > schedule() > > The most straightforward solution seems to be to invert the ordering of > the set_current_state and kthread_should_stop. > > The issue has been noticed during reboot test on a 3.0 based kernel but > the current code seems to be affected in the same way. > > Cc: stable # 3.6+ > Reported-and-Debugged-by: Mike Mayer > Signed-off-by: Michal Hocko > --- > drivers/scsi/scsi_error.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c > index 6457a8a0db9c..2c0a817d5dbe 100644 > --- a/drivers/scsi/scsi_error.c > +++ b/drivers/scsi/scsi_error.c > @@ -2169,8 +2169,11 @@ int scsi_error_handler(void *data) > * We never actually get interrupted because kthread_run > * disables signal delivery for the created thread. > */ > - while (!kthread_should_stop()) { > + while (true) { > set_current_state(TASK_INTERRUPTIBLE); > + if (kthread_should_stop()) > + break; > + > if ((shost->host_failed == 0 && shost->host_eh_scheduled == 0) || > shost->host_failed != atomic_read(&shost->host_busy)) { > SCSI_LOG_ERROR_RECOVERY(1, > Reviewed-by: Hannes Reinecke Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg)