Winbind using 100% CPU

[Andreas Schneider]

On Tuesday 16 April 2013 15:53:35 Jim McDonough wrote:
> 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, can you port this patch to master and ask Dylan to run with the patch so 
we get a full backtrace?


	-- andreas

-- 
Andreas Schneider                   GPG-ID: F33E3FC6
Samba Team                             asn at samba.org
www.samba.org