Re: Processes stuck on D state on Dual Opteron

[Nick Piggin <nickpiggin@yahoo.com.au>]

Claudio Martins wrote:
> On Sunday 10 April 2005 03:47, Andrew Morton wrote:
> 
>>Suggest you boot with `nmi_watchdog=0' to prevent the nmi watchdog from
>>cutting in during long sysrq traces.
>>
>>Also, capture the `sysrq-m' output so we can see if the thing is out of
>>memory.
> 
> 
>   Hi Andrew,
> 
>   Thanks for the tip. I booted with nmi_watchdog=0 and was able to get a full 
> sysrq-t as well as a sysrq-m. Since it might be a little too big for the 
> list, I've put it on a text file at:
> 
>  http://193.136.132.235/dl145/dump1-2.6.12-rc2.txt
> 

OK, you _may_ be out of memory here (depending on what the lower zone
protection for DMA ends up as), however you are well above all the
"emergency watermarks" in ZONE_NORMAL. Also:

>  I also made a run with the mempool-can-fail patch from Nick Piggin. With this 
> I got some nice memory allocation errors from the md threads when the trouble 
> started. The dump (with sysrq-t and sysrq-m included) is at:
> 
>  http://193.136.132.235/dl145/dump2-2.6.12-rc2-nick1.txt
> 

This one shows plenty of memory. The allocation failure messages are
actually a good thing, and show that my patch is sort of working. I
have reworked it a bit so they won't show up though.

So probably not your common or garden memory deadlock.

The common theme seems to be: try_to_free_pages, swap_writepage,
mempool_alloc, down/down_failed in .text.lock.md. Next I would suspect
md/raid1 - maybe some deadlock in an uncommon memory allocation
failure path?

I'll see if I can reproduce it here.

-- 
SUSE Labs, Novell Inc.