Agon S. Buchholz wrote:
Somehow requests to MediaWiki started a few days ago to interfere with the other services operation; e.g., when I'm requesting a page from MediaWiki (e.g. Front Page) and concurrently try to save an article in Drupal, the server does neither deliver the FrontPage from MediaWiki, nor save the article in Drupal (I'm waiting for approx. 10 minutes and usually cancel then the operation by pressing "Esc" in the browser). At this moment, all apache2 proecess dissapear from top/htop and no other requests to either Drupal or MediaWiki are served in any way. As it seeems, MediaWiki started for an unknown reason to kill apache2 in the setup im running.
It sounds like you're running a threaded MPM and PHP is segfaulting. To avoid having MediaWiki interfere with other apps, use the prefork MPM whenever you are using PHP. This is strongly recommended by the PHP manual.
I believe I have written a post or two in the past about debugging and fixing segfaults. I'll repeat some basic principles here in brief.
The first thing to try is the voodoo magic method: change versions of things randomly until it starts working. Disable suspicious PHP extensions. Upgrade or downgrade PHP. Upgrade MediaWiki. Because obvious, reproducible segfaults are usually fixed in PHP or worked around in MediaWiki, it's the rare ones that people usually see, which arise from special combinations of buggy software.
If you're a programmer, then tracing down MediaWiki's call tree to find the segfaulting function, or examining the backtrace in gdb, may produce results.
-- Tim Starling