Premature end of script headers / Signal 11
I have a rather "bloated" WordPress install that is throwing some errors with apache + mod_Fcgid + apc.
I have several other WordPress sites running under this configuration with no issues, but this particular site randomly throws "internal error" in the admin interface and spits out logs like:
[Thu Mar 07 03:37:06 2013] [error] [client 1.2.3.4] Premature end of script headers: php5-fcgi, referer: http://www.example.com/wp-admin/themes.php
[Thu Mar 07 03:37:08 2013] [error] mod_fcgid: process /home/example.com/docs/php5-fcgi(30772) exit(communication error), get unexpected signal 11
[Thu Mar 07 03:37:24 2013] [error] mod_fcgid: process /home/example.com/docs/php5-fcgi(31408) exit(communication error), get unexpected signal 11
[Thu Mar 07 03:37:28 2013] [warn] [client 1.2.3.4] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: http://www.example.com/wp-admin/themes.php
[Thu Mar 07 03:37:28 2013] [error] [client 1.2.3.4] Premature end of script headers: php5-fcgi, referer: http://www.example.com/wp-admin/themes.php
[Thu Mar 07 03:37:29 2013] [error] mod_fcgid: process /home/example.com/docs/php5-fcgi(31410) exit(communication error), get unexpected signal 11
[Thu Mar 07 03:38:31 2013] [warn] [client 1.2.3.4] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: http://www.example.com/wp-admin/widgets.php
[Thu Mar 07 03:38:31 2013] [error] [client 1.2.3.4] Premature end of script headers: php5-fcgi, referer: http://www.example.com/wp-admin/widgets.php
[Thu Mar 07 03:38:34 2013] [error] mod_fcgid: process /home/example.com/docs/php5-fcgi(31412) exit(communication error), get unexpected signal 11
I have set the below values for mod_fcgid:
FcgidMaxRequestInMem 131072
FcgidBusyTimeout 3600
FcgidIOTimeout 600
Any suggestions on what else to adjust?
Update
It looks like the issue only happens when APC is enabled. If I disable APC, all is well. And it is not the same page that throws the error.
Answer
Sounds to me like you are missing a } somewhere, but you haven't really given much to work with. I doubt it's an issue with FastCGI itself.
If you disable all plugins, does the error go away? If so, re-enable them one at a time until you find culprit.
Also, try switching to the default wordpress theme. You'll need to do a little more troubleshooting before you can narrow it down.