(Resending; mailer rejected it ...)
On 05/27/2014 08:08 AM, Bart Van Assche wrote:
On 05/27/14 07:40, Hannes Reinecke wrote:
On 05/26/2014 05:14 PM, Bart Van Assche wrote:
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index f17aa7a..5232583 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -193,7 +193,7 @@ scsi_abort_command(struct scsi_cmnd *scmd)
SCSI_LOG_ERROR_RECOVERY(3,
scmd_printk(KERN_INFO, scmd,
"scmd %p previous abort failed\n", scmd));
- cancel_delayed_work(&scmd->abort_work);
+ WARN_ON_ONCE(delayed_work_pending(&scmd->abort_work));
return FAILED;
}
The first bit is okay, the second isn't.
The second bit is for these cases where the abort got scheduled (in
scsi_abort_command()), but the workqueue didn't get executed by the time
the next timeout occured.
I know, highly unlikely, but there is no safeguarding that it _cannot_
happen.
So the second cancel_delayed_work() has to stay.
But how could that next timeout occur while abort_work is still pending
? The block layer removes a request from the timeout list before
invoking the timeout handler (see also blk_rq_check_expired()). This
means that no block layer timers are active after abort_work has been
scheduled and before scmd_eh_abort_handler() is called. This also means
that a second timeout can only occur after a SCSI command has been
reinserted to a SCSI device queue. And such a reinsertion can only occur
after scmd_eh_abort_handler() has started. The pending bit is cleared
from a work struct before the associated handler is invoked. This is why
I think the above cancel_delayed_work() statement is not necessary. Or
did I perhaps overlook something ?
Hmm. Okay, convinced.
Acked-by: Hannes Reinecke <hare@xxxxxxx>
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@xxxxxxx +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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