From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:36816 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751881AbbJMTGh (ORCPT ); Tue, 13 Oct 2015 15:06:37 -0400 Subject: Patch "scsi: fix scsi_error_handler vs. scsi_host_dev_release race" has been added to the 4.2-stable tree To: mhocko@suse.com, JBottomley@Odin.com, Mike.Meyer@teradata.com, dan.j.williams@intel.com, gregkh@linuxfoundation.org, hare@suse.de Cc: , From: Date: Tue, 13 Oct 2015 12:03:13 -0700 Message-ID: <14447629932548@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled scsi: fix scsi_error_handler vs. scsi_host_dev_release race to the 4.2-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: scsi-fix-scsi_error_handler-vs.-scsi_host_dev_release-race.patch and it can be found in the queue-4.2 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 537b604c8b3aa8b96fe35f87dd085816552e294c Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Thu, 27 Aug 2015 20:16:37 +0200 Subject: scsi: fix scsi_error_handler vs. scsi_host_dev_release race From: Michal Hocko commit 537b604c8b3aa8b96fe35f87dd085816552e294c upstream. 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. [jejb: additional comment added] Reported-and-debugged-by: Mike Mayer Signed-off-by: Michal Hocko Reviewed-by: Dan Williams Reviewed-by: Hannes Reinecke Signed-off-by: James Bottomley Signed-off-by: Greg Kroah-Hartman --- drivers/scsi/scsi_error.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) --- a/drivers/scsi/scsi_error.c +++ b/drivers/scsi/scsi_error.c @@ -2169,8 +2169,17 @@ 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) { + /* + * The sequence in kthread_stop() sets the stop flag first + * then wakes the process. To avoid missed wakeups, the task + * should always be in a non running state before the stop + * flag is checked + */ 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, Patches currently in stable-queue which might be from mhocko@suse.com are queue-4.2/scsi-fix-scsi_error_handler-vs.-scsi_host_dev_release-race.patch