On Thu, 2008-09-11 at 20:35 +0200, Jens Axboe wrote:
> On Thu, Sep 11 2008, James Bottomley wrote:
> > I just noticed this with a rather finickey SAS system I have. It's got
> > a SATA DVD attached over an expander. Periodically the DVD just hangs
> > up, so we wait for the timeout and then send a phy reset which clears
> > it.
> >
> > What I'm seeing with the new block timer code is that the timer never
> > expires. I can dig some more into this, but if you wanted to test it as
> > well, the timer code is easy to excite. Just throw away one command in
> > every 128 or so in the queuecommand routine of your favourite HBA
> > driver.
>
> James, I've seen a few oddities as well, I'll be beating on it tomorrow
> again to shake out the last bug(s).
Actually, turns out it's nothing to do with block timeouts, it's a
target reset bug.
This loop:
for (id = 0; id <= shost->max_id; id++) {
Never terminates if shost->max_id is set to ~0, like aic94xx does.
It's also pretty inefficient since you mostly have compact target
numbers, but the max_id can be very high. The best way would be to sort
the recovery list by target id and skip them if they're equal, but even
a worst case O(N^2) traversal is probably OK here.
James
---
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index ad019ec..94ed262 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -1065,10 +1065,10 @@ static int scsi_eh_target_reset(struct Scsi_Host *shost,
struct list_head *done_q)
{
struct scsi_cmnd *scmd, *tgtr_scmd, *next;
- unsigned int id;
+ unsigned int id = 0;
int rtn;
- for (id = 0; id <= shost->max_id; id++) {
+ do {
tgtr_scmd = NULL;
list_for_each_entry(scmd, work_q, eh_entry) {
if (id == scmd_id(scmd)) {
@@ -1076,8 +1076,18 @@ static int scsi_eh_target_reset(struct Scsi_Host *shost,
break;
}
}
+ if (!tgtr_scmd) {
+ /* not one exactly equal; find the next highest */
+ list_for_each_entry(scmd, work_q, eh_entry) {
+ if (scmd_id(scmd) > id &&
+ (!tgtr_scmd ||
+ scmd_id(tgtr_scmd) > scmd_id(scmd)))
+ tgtr_scmd = scmd;
+ }
+ }
if (!tgtr_scmd)
- continue;
+ /* no more commands, that's it */
+ break;
SCSI_LOG_ERROR_RECOVERY(3, printk("%s: Sending target reset "
"to target %d\n",
@@ -1096,7 +1106,8 @@ static int scsi_eh_target_reset(struct Scsi_Host *shost,
" failed target: "
"%d\n",
current->comm, id));
- }
+ id++;
+ } while(id != 0);
return list_empty(work_q);
}
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