Apache crashing with Mutex errors for the Prefork MPM

Symptoms

Apache using the Prefork MPM crashes with errors like the following.

[mpm_prefork:emerg] [pid 20368:tid 20368] (22)Invalid argument: AH00144: couldn't grab the accept mutex

[mpm_prefork:emerg] [pid 20424:tid 20424] (22)Invalid argument: AH00146: couldn't release the accept mutex

Description

This is due to conflicts with the Mutex settings and the Prefork MPM. 

We've opened an internal case for our development team to investigate this further. For reference, the case number is ZC-12790.

This issue was resolved in ea-apache24-config-1.0-198. The following procedure may be used as a workaround if you are unable to update ea-apache24-config to version 1.0-198 or later.

Workarounds

1. Modify the MPM for Apache to something other than Prefork:
   How to change your Apache MPM in WHM
2. Modify the ea_main.local template to use the Previous Mutex definitions
   1. Copy the existing default template to a .local one

      • cp -avp /var/cpanel/templates/apache2_4/ea4_main.default /var/cpanel/templates/apache2_4/ea4_main.local

   2. Modify the ea4_main.local template and replace `Mutex pthread default` with the following

      • Mutex file:[% paths.dir_run %] rewrite-map
        Mutex file:[% paths.dir_run %] ssl-cache

   3. Rebuild the Apache configuration and restart the service:

      • /usr/local/cpanel/scripts/rebuildhttpdconf;/usr/local/cpanel/scripts/restartsrv_httpd --hard