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Date: Sat, 17 Oct 2015 19:04:54 -0700 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Michal Hocko <mhocko@...e.com>, Dan Williams <dan.j.williams@...el.com>, Hannes Reinecke <hare@...e.de>, James Bottomley <JBottomley@...n.com> Subject: [PATCH 3.14 02/79] scsi: fix scsi_error_handler vs. scsi_host_dev_release race 3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Michal Hocko <mhocko@...e.com> 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 <Mike.Meyer@...adata.com> Signed-off-by: Michal Hocko <mhocko@...e.com> Reviewed-by: Dan Williams <dan.j.williams@...el.com> Reviewed-by: Hannes Reinecke <hare@...e.de> Signed-off-by: James Bottomley <JBottomley@...n.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- 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 @@ -2149,8 +2149,17 @@ 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, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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