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From fredk2 <fre...@gmail.com>
Subject [users@httpd] Deadlocks with Apache mpm worker and mod_jk
Date Thu, 15 Jan 2009 19:46:17 GMT

Hi,

I was doing some stress test (with apache ab, 100 users, 100K requests) to
compare an Apache prefork and worker mpm.  The test url is a simple hello
servlet on Tomcat 6.0.x via mod_jk. On my Solaris 10 server with only the
Apache with worker mpm I see following error messages in my jk log:

Apache/2.2.11 (Unix) with mod_jk/1.2.26 on Solaris 10.

. . .
[Thu Jan 08 11:42:28 2009] [error] (45)Deadlock situation detected/avoided:
apr_global_mutex_lock(jk_log_lock) failed
[Thu Jan 08 11:42:28 2009] [error] (45)Deadlock situation detected/avoided:
apr_global_mutex_lock(jk_log_lock) failed
[Thu Jan 08 11:42:28 2009] [error] (45)Deadlock situation detected/avoided:
apr_global_mutex_lock(jk_log_lock) failed
[Thu Jan 08 11:42:28 2009] [error] (45)Deadlock situation detected/avoided:
apr_global_mutex_lock(jk_log_lock) failed
[Thu Jan 08 11:42:28 2009] [error] (45)Deadlock situation detected/avoided:
apr_global_mutex_lock(jk_log_lock) failed
[Thu Jan 08 11:42:28 2009] [error] (45)Deadlock situation detected/avoided:
apr_global_mutex_lock(jk_log_lock) failed
[Thu Jan 08 11:42:29 2009] [error] (45)Deadlock situation detected/avoided:
apr_global_mutex_lock(jk_log_lock) failed
[Thu Jan 08 11:42:29 2009] [emerg] (45)Deadlock situation detected/avoided:
apr_proc_mutex_lock failed. Attempting to shutdown process gracefully.
[Thu Jan 08 11:42:29 2009] [error] (45)Deadlock situation detected/avoided:
apr_global_mutex_lock(jk_log_lock) failed
. . .

these errors do not appear to have an impact on the test - the test
completes with reasonable results < 58 ms and the jk log file seems
complete.

I can suppress the errors by choosing another Mutex in the Apache directive
AcceptMutex, such as sysvsem or pthread.  For Solaris 10 the default mutex
for worker MPM is fcntl.  Setting the Mutex sysvsem (default on RedHat Linux
build) marginally improves the request time.

Can someone explain what exactly these errors means? when does it occur?
I would have expect a detected/avoided to be a [warn] instead of an [error].  

Also does anybody have an idea/experience with Solaris 10 mutexes - what is
the better mutex?  sysvsme, posixsem, pthread **?

Your comments will be appreciated.

Many thanks, Fredk

** http://markmail.org/message/ta46uav3hleqbya3 seems to say never to use
posixsem, pthread
-- 
View this message in context: http://www.nabble.com/Deadlocks-with-Apache-mpm-worker-and-mod_jk-tp21485344p21485344.html
Sent from the Apache HTTP Server - Users mailing list archive at Nabble.com.


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