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Posted to bugs@httpd.apache.org by bu...@apache.org on 2015/08/20 16:58:44 UTC
[Bug 53999] Deadlock between
procmgr_send_spawn_cmd()/proctable_lock() in mod_fcgid and listener_thread()
in worker_mpm
https://bz.apache.org/bugzilla/show_bug.cgi?id=53999
thomas@shadowweb.org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Resolution|FIXED |---
--- Comment #3 from thomas@shadowweb.org ---
Unfortunately I am able to reproduce the problem with a Debian Jessie
installation.
Using mpm_worker and mod_fcgid the following messages begin to appear in the
error log under heavy load (also triggerable via ab -c15):
[Mon Aug 17 15:21:13.509763 2015] [fcgid:emerg] [pid 21497:tid 139901035079424]
(35)Resource deadlock avoided: [client XXX.XXX.XXX.XXX:38964] mod_fcgid: can't
get pipe mutex
[...]
[Mon Aug 17 15:22:49.387129 2015] [fcgid:emerg] [pid 22016:tid 139900959545088]
(35)Resource deadlock avoided: [client XXX.XXX.XXX.XXX:39590] mod_fcgid: can't
lock process table in pid 22016
[Mon Aug 17 15:22:53.479254 2015] [fcgid:emerg] [pid 22047:tid 139901035079424]
(35)Resource deadlock avoided: [client XXX.XXX.XXX.XXX:39617] mod_fcgid: can't
lock process table in pid 22047
[...]
At the same time, gracefully terminated FCGI processes don't get
wait()/waitpid() ed and are left in a zombie state by Apache until
FcgidMaxProcessesPerClass are used up (then 503 errors).
Using mpm_event I was also able to reproduce the problem, however, the
frequency was greatly reduced.
The only solution for me up to this point is using mpm_prefork, with which the
error is not reproductible at all.
Apache version: 2.4.10
mod_fcgid version: 2.3.9
Linux kernel version: 3.16.7
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