Messages in this thread Patch in this message | | | From | Kamal Mostafa <> | Subject | [PATCH 3.13.y-ckt 60/85] scsi: fix scsi_error_handler vs. scsi_host_dev_release race | Date | Tue, 20 Oct 2015 14:35:16 -0700 |
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3.13.11-ckt28 -stable review patch. If anyone has any objections, please let me know.
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From: Michal Hocko <mhocko@suse.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@teradata.com> Signed-off-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: James Bottomley <JBottomley@Odin.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- 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 c6dcbe6..790f716 100644 --- a/drivers/scsi/scsi_error.c +++ b/drivers/scsi/scsi_error.c @@ -2025,8 +2025,17 @@ 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, -- 1.9.1
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