NFS deadlock on 9.2-Beta1

[Oliver Pinter]

On 8/20/13, J David <j.david.lists at gmail.com> wrote:
> On Thu, Aug 15, 2013 at 5:39 PM, Rick Macklem <rmacklem at uoguelph.ca> wrote:
>> Have you been able to pass the debugging info on to Kostik?
>>
>> It would be really nice to get this fixed for FreeBSD9.2.
>
> You're probably not talking to me, but headway here is slow.  At our
> location, we have been continuing to test releng/9.2 extensively, but
> with r250907 reverted.  Since reverting it solves the issue, and since
> there haven't been any further changes to releng/9.2 that might also
> resolve this issue, re-applying r250907 is perceived here as un-fixing
> a problem.  Enthusiasm for doing so is correspondingly low, even if
> the purpose is to gather debugging info. :(
>
> However, after finally having clearance to test releng/9.2 r254540
> with r250907 included and with DDB on five nodes.  The problem cropped
> up in about an hour.  Two threads in one process deadlocked, was
> perfect.  Got it into DDB and saw the stack trace was scrolling off so
> there was no way to copy it by hand.  Also, the machine's disk is
> smaller than physical RAM, so no dump file. :(
>
> Here's what is available so far:
>
> db> show proc 33362
>
> Process 33362 (httpd) at 0xcd225b50:
>
>  state: NORMAL
>
>  uid: 25000 gids: 25000
>
>  parent: pid 25104 at 0xc95f92d4
>
>  ABI: FreeBSD ELF32
>
>  arguments: /usr/local/libexec/httpd
>
>  threads: 3
>
> 100405 D newnfs 0xc9b875e4 httpd
>
> 100393 D pgrbwt 0xc43a30c0 httpd
>
> 100755 S uwait 0xc84b7c80 httpd
>
>
> Not much to go on. :(  Maybe these five can be configured with serial
> consoles.

try this with serial console:

host # script debug-output-file
host # cu -s 9600 -l /dev/ttyU0
~^B
KDB: enter: Break to debugger
[ thread pid 11 tid 100005 ]
Stopped at      kdb_alt_break_internal+0x17f:   movq    $0,kdb_why
db>   show msgbuf

...
~.
^D

>
> So, inquiries are continuing, but the answer to "does this still
> happen on 9.2-RC2?" is definitely yes.
>
> Thanks!
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