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authorMichal Hocko <mhocko@suse.com>2015-08-27 20:16:37 +0200
committerJames Bottomley <JBottomley@Odin.com>2015-09-06 12:05:45 -0700
commit537b604c8b3aa8b96fe35f87dd085816552e294c (patch)
tree62d373c3c0b74bfc2c317598edc59acb3daf28c6
parent420fa2118c020a005e9f0311c1e0b27414306618 (diff)
downloadlwn-537b604c8b3aa8b96fe35f87dd085816552e294c.tar.gz
lwn-537b604c8b3aa8b96fe35f87dd085816552e294c.zip
scsi: fix scsi_error_handler vs. scsi_host_dev_release race
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] Cc: <stable@vger.kernel.org> # 3.6+ 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>
-rw-r--r--drivers/scsi/scsi_error.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 410911c31c67..b5bbc122c414 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -2179,8 +2179,17 @@ 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,