httpd-users mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Boyle Owen" <>
Subject RE: mod_ssl mutex and session cache problem
Date Wed, 26 Jun 2002 14:10:34 GMT
>From: Rok Zevnik []
>I have a problem with mod_ssl running apache 2.0.36 on Linux Debian.
>The ssl server hangs after couple of HTTPS requests and i have to restart it.
>In log file I get these two warnings when the connection hangs:
>[warn]  Failed to acquire global mutex lock
>I found out that if I change the settings in ssl.conf from
>SSLSessionCache         dbm:logs/ssl_scache
>SSLSessionCacheTimeout  30
>SSLSessionCache        none
>then everything works OK.

Remember that apache is a multi-daemon server and that any given request can be served by
any of several processes. However, it is sometimes useful for some information (in this case
the SSL session-key) to be available to all daemons. So mod_ssl puts the session key in a
cache which is shared. Mutex is the mechanism which prevents various instances of apache from
editing this information (mutual exclusion locking). 

As you can see, this is all getting a bit complicated and to be honest I don't understand
it fully myself. To fix it properly will require understanding your semaphores setup which
is way beyond the scope of this list. Try the mod_ssl list for more info (

In any case, your workaround of simply switching off session-caching will work with the proviso
that every request will have to restablish an SSL session. This will hit performance if you
have a busy server.


Owen Boyle.

To unsubscribe, e-mail:
For additional commands, e-mail:

View raw message