James Bottomley wrote:
> On Tue, 2006-05-16 at 11:41 -0400, Jeff Garzik wrote:
>> I can't see a case _in libata operation_ where a set of circumstances
>> arises that causes missed wakeups, can you elaborate?
>
> This is scsi_eh_wakeup():
>
> void scsi_eh_wakeup(struct Scsi_Host *shost)
> {
> if (shost->host_busy == shost->host_failed) {
> wake_up_process(shost->ehandler);
>
> so if you try a wakeup with no failed commands and the host still busy,
> nothing happens.
It's handled the same way shost->host_failed is handled.
scsi_device_unbusy() wakes it up when the condition is met.
void scsi_device_unbusy(struct scsi_device *sdev)
{
struct Scsi_Host *shost = sdev->host;
unsigned long flags;
spin_lock_irqsave(shost->host_lock, flags);
shost->host_busy--;
if (unlikely(scsi_host_in_recovery(shost) &&
(shost->host_failed || shost->host_eh_scheduled)))
scsi_eh_wakeup(shost);
spin_unlock(shost->host_lock);
spin_lock(sdev->request_queue->queue_lock);
sdev->device_busy--;
spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
}
[--snip--]
>>> 2) This scsi_req_abort_cmd() is fundamentally the wrong logic.
>>> Everything else is communicated back as a result code from the command
>>> in done(). This should be no different ... A status return of
>>> DID_FAILED which scsi_decide_disposition() always translates to FAILED
>>> would seem to do exactly what you want without all the overhead.
>> Inigo sez[1]: I do not think "fundamentally wrong" means what you think
>> it means.
Currently, there is no reliable way to trigger DID_FAILED
unconditionally. I thought about adding some host code or whatever to
force it but it felt too hackish and went with the
scsi_eh_schedule_scmd(). Then, Luben suggested scsi_req_abort_cmd(), so
that's what I've ended up with.
>> You miss the fact that the timer may have already fired, in which
>> completing a command gets you...... not a damned thing. scsi_done()
>> will simply return, if the timeout has fired. This has always been an
>> annoying problem to work around.
>
> No ... in that case the eh is already active, and your API does this:
>
> void scsi_req_abort_cmd(struct scsi_cmnd *cmd)
> {
> if (!scsi_delete_timer(cmd))
> return;
> ^^^^^^^
> scsi_times_out(cmd);
> }
>
> Which likewise does nothing if the timer has already fired, so they both
> have the same effect.
--
tejun
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