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| author | Michal Hocko <mhocko@suse.com> | 2015-08-27 20:16:37 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-10-22 14:49:14 -0700 |
| commit | 4a248398eb8fab3b85bda9ba59a7834ea124a367 (patch) | |
| tree | e6c53067102bc92125284acb3716d45ad5247411 /drivers | |
| parent | 0df8a7a1a277c20fa8e55afbdbdacd7eb7c2aed4 (diff) | |
| download | lwn-4a248398eb8fab3b85bda9ba59a7834ea124a367.tar.gz lwn-4a248398eb8fab3b85bda9ba59a7834ea124a367.zip | |
scsi: fix scsi_error_handler vs. scsi_host_dev_release race
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>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/scsi/scsi_error.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c index 6457a8a0db9c..bf3d801ac5f9 100644 --- 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, |