If there is a race between scsi_done() and scsi_timeout() and if
scsi_timeout() loses the race, scsi_timeout() should not reset the
request timer. Hence change the return value for this case from
BLK_EH_RESET_TIMER into BLK_EH_DONE.
Although the block layer holds a reference on a request (req->ref) while
calling a timeout handler, restarting the timer (blk_add_timer()) while
a request is being completed is racy.
Cc: Keith Busch <kbusch@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Cc: John Garry <john.garry@xxxxxxxxxx>
Cc: Mike Christie <michael.christie@xxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Reported-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Fixes: 065990bd198e ("scsi: set timed out out mq requests to complete")
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
drivers/scsi/scsi_error.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 16bd0adc2339..d1b07ff64a96 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -343,19 +343,11 @@ enum blk_eh_timer_return scsi_timeout(struct request *req)
if (rtn == BLK_EH_DONE) {
/*
- * Set the command to complete first in order to prevent a real
- * completion from releasing the command while error handling
- * is using it. If the command was already completed, then the
- * lower level driver beat the timeout handler, and it is safe
- * to return without escalating error recovery.
- *
- * If timeout handling lost the race to a real completion, the
- * block layer may ignore that due to a fake timeout injection,
- * so return RESET_TIMER to allow error handling another shot
- * at this command.
+ * If scsi_done() has already set SCMD_STATE_COMPLETE, do not
+ * modify *scmd.
*/
if (test_and_set_bit(SCMD_STATE_COMPLETE, &scmd->state))
- return BLK_EH_RESET_TIMER;
+ return BLK_EH_DONE;
if (scsi_abort_command(scmd) != SUCCESS) {
set_host_byte(scmd, DID_TIME_OUT);
scsi_eh_scmd_add(scmd);
