scsi: mpt3sas: Fix deadlock while cancelling the running firmware event

Do not cancel current running firmware event work if the event type is
different from MPT3SAS_REMOVE_UNRESPONDING_DEVICES.  Otherwise a deadlock
can be observed while cancelling the current firmware event work if a hard
reset operation is called as part of processing the current event.

Link: https://lore.kernel.org/r/20210518051625.1596742-2-suganath-prabu.subramani@broadcom.com
Signed-off-by: Suganath Prabu S <suganath-prabu.subramani@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
index d00aca3..79e34b5 100644 (file)
--- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
@@ -3697,6 +3697,28 @@ _scsih_fw_event_cleanup_queue(struct MPT3SAS_ADAPTER *ioc)
        ioc->fw_events_cleanup = 1;
        while ((fw_event = dequeue_next_fw_event(ioc)) ||
             (fw_event = ioc->current_event)) {
+
+               /*
+                * Don't call cancel_work_sync() for current_event
+                * other than MPT3SAS_REMOVE_UNRESPONDING_DEVICES;
+                * otherwise we may observe deadlock if current
+                * hard reset issued as part of processing the current_event.
+                *
+                * Orginal logic of cleaning the current_event is added
+                * for handling the back to back host reset issued by the user.
+                * i.e. during back to back host reset, driver use to process
+                * the two instances of MPT3SAS_REMOVE_UNRESPONDING_DEVICES
+                * event back to back and this made the drives to unregister
+                * the devices from SML.
+                */
+
+               if (fw_event == ioc->current_event &&
+                   ioc->current_event->event !=
+                   MPT3SAS_REMOVE_UNRESPONDING_DEVICES) {
+                       ioc->current_event = NULL;
+                       continue;
+               }
+
                /*
                 * Wait on the fw_event to complete. If this returns 1, then
                 * the event was never executed, and we need a put for the