Messages in this thread Patch in this message | | | From | mhocko@kernel ... | Subject | [PATCH] scsi: fix scsi_error_handler vs. scsi_host_dev_release race | Date | Thu, 27 Aug 2015 20:16:37 +0200 |
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From: Michal Hocko <mhocko@suse.com>
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.
Cc: stable # 3.6+ Reported-and-Debugged-by: Mike Mayer <Mike.Meyer@teradata.com> Signed-off-by: Michal Hocko <mhocko@suse.com> --- drivers/scsi/scsi_error.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c index 6457a8a0db9c..2c0a817d5dbe 100644 --- a/drivers/scsi/scsi_error.c +++ b/drivers/scsi/scsi_error.c @@ -2169,8 +2169,11 @@ 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) { 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, -- 2.5.0
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