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| author | Michal Hocko <mhocko@suse.com> | 2015-08-27 20:16:37 +0200 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2015-10-27 10:18:20 +0100 |
| commit | ee2101730dae3748e94a3032091c8ecb0077e49e (patch) | |
| tree | a9112de470c4b08c2c2808721d9e318d3abbcaa7 | |
| parent | 7272edcb2309fcfe792878898c4214548cc4a908 (diff) | |
| download | lwn-ee2101730dae3748e94a3032091c8ecb0077e49e.tar.gz lwn-ee2101730dae3748e94a3032091c8ecb0077e49e.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: Jiri Slaby <jslaby@suse.cz>
| -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 066e3198838d..ff2689d01209 100644 --- a/drivers/scsi/scsi_error.c +++ b/drivers/scsi/scsi_error.c @@ -1906,8 +1906,17 @@ 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, |