On Mon, 31 Mar 2014, James Bottomley wrote:
> > The actual question is whether it's worth aborting the same command
> > a second time.
> > In principle any reset (like LUN reset etc) should clear the
> > command, too.
> > And the EH abort functionality is geared around this.
> > If, for some reason, the transport layer / device driver
> > requires a command abort to be send then sure, we need
> > to accommodate for that.
>
> We already discussed this (that was my first response too). USB needs
> all outstanding commands aborted before proceeding to reset. I'm
> starting to think the actual way to fix this is to reset the abort
> scheduled only if we send something else, so this might be a better fix.
>
> It doesn't matter if we finish a command with abort scheduled because
> the command then gets freed and the flags cleaned.
>
> We can take our time with this because the other two patches, which I
> can send separately fix the current deadlock (we no longer send an
> unaborted request sense before the reset), and it can go via rc fixes.
>
> James
>
> ---
>
> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> index 771c16b..3cfd2bf 100644
> --- a/drivers/scsi/scsi_error.c
> +++ b/drivers/scsi/scsi_error.c
> @@ -1007,6 +1007,12 @@ static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd,
> unsigned char *cmnd,
> const unsigned long stall_for = msecs_to_jiffies(100);
> int rtn;
>
> + /*
> + * We're sending another command we'll need to abort, so reset the
> + * abort scheduled flag on the real command before we save its state
> + */
> + scmd->eh_eflags &= ~SCSI_EH_ABORT_SCHEDULED;
> +
> retry:
> scsi_eh_prep_cmnd(scmd, &ses, cmnd, cmnd_size, sense_bytes);
> shost->eh_action = &done;
I don't know if Hannes will like this, but I don't think it is right.
This is not the retry pathway that's causing problems; that pathway
begins where scmd_eh_abort_handler() calls scsi_queue_insert().
Now, that call is already guarded by this test:
if (... && (++scmd->retries <= scmd->allowed)) {
which would seem to prevent the infinite loop that Hannes was concerned
about. So maybe the 1/3 patch posted a couple of days ago is the best
solution after all.
Alan Stern
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