Winbind using 100% CPU

[Jim McDonough]

On Tue, Apr 16, 2013 at 2:45 PM, Jeremy Allison <jra at samba.org> wrote:
> On Tue, Apr 16, 2013 at 01:46:14PM -0400, Jim McDonough wrote:
>> On Tue, Apr 16, 2013 at 10:00 AM, Jim McDonough <jmcd at samba.org> wrote:
>> > On Thu, Apr 11, 2013 at 6:59 PM, Jeremy Allison <jra at samba.org> wrote:
>> >> On Thu, Apr 11, 2013 at 09:58:33AM -0400, Dylan Klomparens wrote:
>> >>> (Re-posting on this email list per Jeremy Allison's request.)
>> >>>
>> >>> I am trying to figure out why winbind is using 100% CPU on my file server.
>> >>> I am using Samba version 4.0.4. Everything is fine for a few minutes when I
>> >>> start winbind, however after a while it begins using 100% CPU. I haven't
>> >>> been able to narrow down what triggers this CPU usage spike, but I did
>> >>> attach the GNU debugger to find out what's going on in the process. The
>> >>> backtrace revealed this information:
>> >>>
>> >>> #0  0x000000000041cf30 in _talloc_free at plt ()
>> >>> #1  0x0000000000452320 in winbindd_reinit_after_fork ()
>> >>> #2  0x00000000004524e6 in fork_domain_child ()
>> >>> #3  0x0000000000453585 in wb_child_request_trigger ()
>> >>> #4  0x000000381d2048e2 in tevent_common_loop_immediate () from
>> >>> /lib64/libtevent.so.0
>> >>> #5  0x00007fbed6b98e17 in run_events_poll () from /lib64/libsmbconf.so.0
>> >>> #6  0x00007fbed6b9922e in s3_event_loop_once () from /lib64/libsmbconf.so.0
>> >>> #7  0x000000381d204060 in _tevent_loop_once () from /lib64/libtevent.so.0
>> >>> #8  0x000000000042049a in main ()
>> >>>
>> >>> Apparently it's stuck in the winbindd_reinit_after_fork (and more
>> >>> specifically the _talloc_free function). This code resides in
>> >>> $SOURCE_HOME\source3\winbindd\winbindd_dual.c.
>> >>
>> >> That looks like corrupted memory - probably a loop
>> >> in the talloc tree.
>> > I've got a user who sees this and we're adding the same dlinklist
>> > element twice, creating a loop in the winbind child list.
>> >
>> > I've got a broken wrist so responses take a while, but that's my
>> > current hint.  On 3.6.3 and 3.6.13.
>> >
>>
>> I see this in the parent winbind log.  The last 3 entries are changes
>> I made to the dlist macros within winbind only.  you can see a 2
>> second delay and then a second add of the same item to the child
>> winbind list.  No entries in between (and a production system so there
>> is reluctance to increase the debug level).
>>
>> [2013/03/14 09:08:57.795585,  3]
>> winbindd/winbindd_getpwnam.c:56(winbindd_getpwnam_send)
>>   getpwnam xx+xxxxxxxxx-112$
>> [2013/03/14 09:08:57.796185,  3]
>> winbindd/winbindd_getpwnam.c:56(winbindd_getpwnam_send)
>>   getpwnam xx+yyyyyyy
>> [2013/03/14 09:09:00.077660,  0]
>> winbindd/winbindd_dual.c:1399(fork_domain_child)
>>   adding 0x7ff91105a000 to list at 0x7ff911053510
>> [2013/03/14 09:09:02.435367,  0]
>> winbindd/winbindd_dual.c:1399(fork_domain_child)
>>   adding 0x7ff91105a000 to list at 0x7ff91105a000
>> [2013/03/14 09:09:02.435510,  0] lib/util.c:1117(smb_panic)
>>   PANIC (pid 28628): duplicate
>
> Jim, do your changes lead to a smb_panic on an
> DLIST_ADD of a duplicate ? If so, can you post
> a complete backtrace ?
>
> Jeremy.

 [2013/03/14 09:09:02.437394,  0] lib/util.c:1221(log_stack_trace)
   BACKTRACE: 11 stack frames:
    #0 /usr/sbin/winbindd(log_stack_trace+0x1a) [0x7f02379883ba]
    #1 /usr/sbin/winbindd(smb_panic+0x2b) [0x7f023798848b]
    #2 /usr/sbin/winbindd(+0x10806e) [0x7f02378d206e]
    #3 /usr/sbin/winbindd(+0x1084b5) [0x7f02378d24b5]
    #4 /usr/sbin/winbindd(tevent_common_loop_immediate+0xea) [0x7f023799917a]
    #5 /usr/sbin/winbindd(run_events_poll+0x3b) [0x7f02379973db]
    #6 /usr/sbin/winbindd(+0x1cdb12) [0x7f0237997b12]
    #7 /usr/sbin/winbindd(_tevent_loop_once+0x90) [0x7f0237997f10]
    #8 /usr/sbin/winbindd(main+0x7db) [0x7f02378aa13b]
    #9 /lib64/libc.so.6(__libc_start_main+0xe6) [0x7f0234a2ec36]
    #10 /usr/sbin/winbindd(+0xdd839) [0x7f02378a7839]


Unfortunately their core file doesn't seem quite right...this was out
of their logs and I'm having trouble with the core, but this fscking
splint keeps me moving at a snail's pace


--
Jim McDonough
Samba Team
SUSE labs
jmcd at samba dot org
jmcd at themcdonoughs dot org