> Rainer Canavan <rainer.canavan <at> sevenval.com> writes:
>
> > we've got an obscure problem with the apache httpd that was shipped
> > with CentOS 7.2. We perform automatic builds and updates via cron,
> > and, since the update to CentOS 7.2. The update script is triggered by
> > cron and stops, yum updates and starts the httpd. When the next cron
> > job that is run as the same user as the httpd (not the update job)
> > terminates, the httpd frequently fails, starting with a AH00273:
> > apr_proc_mutex_lock failed message, and then a never ending loop of
> > AH00272 messages, one from each httpd process that is forked, until
> > the listener process is stopped.
>
> > Does anyone have any ideas what may cause these mutex errors?
>
> Sorry - no ideas, but I'm having the exact same issue, and have been trying
> for the better part of a week to figure out what is causing this.
Discussed with thumbs on IRC. Setting "Mutex sem" in my httpd.conf appears
to be a work-around for this. Otherwise, it was unset, and would apparently
default to "Mutex default".
He suspected that "the apr package was botched by the RHEL maintainers".
However, when I tried my compile-from-source work-around, it required a
source include of both apr and apr-util, so I would think that could be
discounted? Or possibly lead to a worse issue in something lower-level
within RHEL/CentOS? But still worked-around by using sem - and would
further explain why something like cron seems to need to be involved to
reproduce?
Frustratingly, reproducing this appears to be hit-and-miss. Following-up on
my previous reply, I further did install mod_ssl and cloned over my complete
configurations from the problem instance to my test instance, and was still
unable to reproduce on a 2nd box with what I believe to be an identical
build and configuration.
We were curious if there was a way to determine if there was a way to know
which implementation was being selected by default (and problematic), as
both SYSVSEM and PTHREAD were defined in httpd -V (as shown below)? I also
checked my compile-from-source work-around attempt, and using the
Apache-provided defaults, everything related to the Mutex appeared to be
identical. (Same 2 defines shown in httpd -V, and not explicit Mutex
declaration in my httpd configuration files.)
Is there anything further I can provide to help with this, even though it
appears I may have a successful work-around? (Should a bug be opened for
this on a tracker somewhere?)
$ httpd -V
Server version: Apache/2.4.6 (CentOS)
Server built: Nov 19 2015 21:43:13
Server's Module Magic Number: 20120211:24
Server loaded: APR 1.4.8, APR-UTIL 1.5.2
Compiled using: APR 1.4.8, APR-UTIL 1.5.2
Architecture: 64-bit
Server MPM: worker
threaded: yes (fixed thread count)
forked: yes (variable process count)
Server compiled with....
-D APR_HAS_SENDFILE
-D APR_HAS_MMAP
-D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
-D APR_USE_SYSVSEM_SERIALIZE
-D APR_USE_PTHREAD_SERIALIZE
-D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
-D APR_HAS_OTHER_CHILD
-D AP_HAVE_RELIABLE_PIPED_LOGS
-D DYNAMIC_MODULE_LIMIT=256
-D HTTPD_ROOT="/etc/httpd"
-D SUEXEC_BIN="/usr/sbin/suexec"
-D DEFAULT_PIDLOG="/run/httpd/httpd.pid"
-D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
-D DEFAULT_ERRORLOG="logs/error_log"
-D AP_TYPES_CONFIG_FILE="conf/mime.types"
-D SERVER_CONFIG_FILE="conf/httpd.conf"
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