Re: 5.3-RELEASE: WARNING - WRITE_DMA interrupt timout

For your information, I applied this patch just now to my kernel. Sorry 
about the delay! I will send an update in a few days once I see if those 
DMA_WRITE warnings are still happening or not.

Zoltan

Poul-Henning Kamp wrote:
> In message <4195E1FF.5090906_at_DeepCore.dk>, 
> =?ISO-8859-1?Q?S=F8ren_Schmidt?= wri
> tes:
>
>
>>>>Timeout is 5 secs, which is a pretty long time in this context IMHO..
>>>
>>>Five seconds counted from when ?
>>
>>Now thats the nasty part :)
>>ATA starts the timeout when the request is issued to the device, so 
>>theoretically the disk could take 4.9999 secs to complete the request and 
>>then the timeout fires before the taskqueue gets its chance at it, but 
>>IMHO thats pretty unlikely...
>
> I find that far more likely than kernel threads being stalled for that
> long.  ATA disks doing bad-block stuff takes several seconds on some
> of the disks I've had my hands on.
>
>>Anyhow, I can just remove the warning from ATA if that makes anyone happy, 
>>since its just a warning and ATA doesn't do anything with it at all.
>>However, IMNHO this points at a problem somewhere that we should better 
>>understand and fix instead.
>
> I would prefer you reset the timer to five seconds in your interrupt
> routine so we can see exactly on which side of that the time is spent.

It would be even better to time how long both ops take and be able to
get that via a sysctl or something (I have that on my TODO list but its
loooong :) ).

Anyhow resetting it is easy (patch against 5.3R):

Index: ata-queue.c
===================================================================
RCS file: /home/ncvs/src/sys/dev/ata/ata-queue.c,v
retrieving revision 1.32.2.5
diff -u -r1.32.2.5 ata-queue.c
--- ata-queue.c 24 Oct 2004 09:27:37 -0000      1.32.2.5
+++ ata-queue.c 13 Nov 2004 10:44:40 -0000
_at__at_ -216,6 +216,9 _at__at_
         ata_completed(request, 0);
      }
      else {
+       if (!dumping)
+           callout_reset(&request->callout, request->timeout * hz,
+                         (timeout_t*)ata_timeout, request);
         if (request->bio && !(request->flags & ATA_R_TIMEOUT)) {
             ATA_DEBUG_RQ(request, "finish bio_taskqueue");
             bio_taskqueue(request->bio, (bio_task_t *)ata_completed,
request);

-- 

-Søren