From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from youngberry.canonical.com ([91.189.89.112]:46500 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755817AbbI3Jws (ORCPT ); Wed, 30 Sep 2015 05:52:48 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Michal Hocko , James Bottomley , Luis Henriques Subject: [PATCH 3.16.y-ckt 077/133] scsi: fix scsi_error_handler vs. scsi_host_dev_release race Date: Wed, 30 Sep 2015 10:50:25 +0100 Message-Id: <1443606681-7124-78-git-send-email-luis.henriques@canonical.com> In-Reply-To: <1443606681-7124-1-git-send-email-luis.henriques@canonical.com> References: <1443606681-7124-1-git-send-email-luis.henriques@canonical.com> Sender: stable-owner@vger.kernel.org List-ID: 3.16.7-ckt18 -stable review patch. If anyone has any objections, please let me know. ------------------ 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: Luis Henriques --- drivers/scsi/scsi_error.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c index f0c7a970547f..48790f1dbf79 100644 --- a/drivers/scsi/scsi_error.c +++ b/drivers/scsi/scsi_error.c @@ -2154,8 +2154,17 @@ 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 != shost->host_busy) { SCSI_LOG_ERROR_RECOVERY(1,