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Subject: mod_http2 and Frequent wake-ups for mpm_event
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From: Stefan Priebe - Profihost AG <s.priebe@profihost.ag>
Cc: Stefan Eissing <stefan.eissing@greenbytes.de>,
 Yann Ylavic <ylavic.dev@gmail.com>
Message-ID: <cd99c46b-ce61-7ed4-0e1e-38b414e78154@profihost.ag>
Date: Wed, 18 Jan 2017 11:33:07 +0100
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archived-at: Wed, 18 Jan 2017 10:33:24 -0000

Hi Stefan,
 Hi Yann,

after applying the event patch to 2.4.25 from
https://bz.apache.org/bugzilla/show_bug.cgi?id=57399.

I'm seeing segfaults in the mod_http2 code. I already bumped mod_http2
to v1.8.8. But the segfaults are still happening.

gdb shows this:
Core was generated by `/usr/local/apache2/bin/httpd -k start'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007fb75242cd45 in apr_pool_cleanup_kill () from
/usr/lib/x86_64-linux-gnu/libapr-1.so.0
(gdb) bt
#0  0x00007fb75242cd45 in apr_pool_cleanup_kill () from
/usr/lib/x86_64-linux-gnu/libapr-1.so.0
#1  0x00007fb75242ce21 in apr_pool_cleanup_run () from
/usr/lib/x86_64-linux-gnu/libapr-1.so.0
#2  0x000000000051f268 in stream_pool_cleanup ()
#3  0x00007fb7327eb270 in ?? ()
#4  0x00007fb730c180a0 in ?? ()
#5  0x00007fb7327eb294 in ?? ()
#6  0x00007fb7309046c0 in ?? ()
#7  0x00007fb730c180a0 in ?? ()
#8  0x0000000030c18028 in ?? ()
#9  0x00007fb730c18028 in ?? ()
#10 0x00007fb75242b9be in apr_pool_destroy () from
/usr/lib/x86_64-linux-gnu/libapr-1.so.0
#11 0x000000000051fe61 in h2_stream_destroy ()
#12 0x0000002d317482d8 in ?? ()
#13 0x00007fb730c180a0 in ?? ()
#14 0x00007fb7327eb300 in ?? ()
#15 0x0000000000507ab7 in stream_done ()
#16 0x0000000000000000 in ?? ()


and or this:
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007fd2e9034014 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0  0x00007fd2e9034014 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
#1  0x00007fd2e94c7036 in ?? () from /usr/lib/x86_64-linux-gnu/libapr-1.so.0
#2  0x00007fd2e94c746f in apr_hash_set () from
/usr/lib/x86_64-linux-gnu/libapr-1.so.0
#3  0x000000000052a238 in h2_ihash_remove ()
#4  0x0000004b00000000 in ?? ()
#5  0x00007fd2c8d60328 in ?? ()
#6  0x00007fd2c97e9300 in ?? ()
#7  0x0000000000506b24 in purge_stream ()
#8  0x00007fd2d82140a0 in ?? ()
#9  0x00007fd2c831e2d8 in ?? ()
#10 0x00007fd20352c0a0 in ?? ()
#11 0x0000004b00000000 in ?? ()
#12 0x00007fd2d82140a0 in ?? ()
#13 0x00007fd2c831e2d8 in ?? ()
#14 0x00007fd2c97e9340 in ?? ()
#15 0x000000000052a18f in ihash_iter ()
#16 0x00007fd2d82140a0 in ?? ()
#17 0x0000000000000004 in ?? ()
#18 0x00007fd2d82140a0 in ?? ()
#19 0x00007fd2c97e93c0 in ?? ()
#20 0x0000000000000000 in ?? ()


Greets,
Stefan

Am 17.01.2017 um 21:53 schrieb Stefan Priebe:
> Hi Yann,
> 
> while testing V6 i'm experiencing segfaults.
> 
> exit signal Segmentation
> 
> server-error.log:
> AH00052: child pid 14110 exit signal Segmentation fault (11)
> 
> currently i'm trying to grab a core dump.
> 
> Greets,
> Stefan
> 
> Am 26.12.2016 um 21:18 schrieb Stefan Priebe - Profihost AG:
>> Am 23.12.2016 um 01:41 schrieb Yann Ylavic:
>>> Hi Stefan,
>>>
>>> On Tue, Dec 20, 2016 at 1:52 PM, Stefan Priebe - Profihost AG
>>> <s.priebe@profihost.ag> wrote:
>>>>
>>>> Today i had another server giving no answers to any requests. apache
>>>> fullstatus did not respond.
>>>
>>> Since v5 of the patch, I committed another related change in trunk,
>>> namely: http://svn.apache.org/r1774538
>>> It's about lingering keepalive connections on graceful restart which
>>> may not cause a wakeup.
>>> Does it help?
>>
>> I'll try that but wanted to rebuild based on http 2.4.25. But your
>> mpm_event_listener_wakeup_bug57399_V5 patch does no longer apply to http
>> 2.2.25. Can you rebase it?
>>
>>>> gdb bt shows this for all httpd childs:
>>>
>>> These backtraces are the ones of the main thread, probably not the
>>> culprit.
>>> What does "thread apply all bt" say?
>>
>> Will redo / save that output next time.
>>
>> Thanks!
>>
>> Greets,
>> Stefan
>>
>>> Regards,
>>> Yann.
>>>