| From 537b604c8b3aa8b96fe35f87dd085816552e294c Mon Sep 17 00:00:00 2001 |
| From: Michal Hocko <mhocko@suse.com> |
| Date: Thu, 27 Aug 2015 20:16:37 +0200 |
| Subject: scsi: fix scsi_error_handler vs. scsi_host_dev_release race |
| |
| 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: Greg Kroah-Hartman <gregkh@linuxfoundation.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, |