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I'm seeing the following error in apache's error_log. It's completely random but when it happens, it prints 10-20 lines in error_log.

Apache: [core:notice] [pid ***] AH00052: child pid *** exit signal Segmentation fault (11)

I'm running Apache 2.4.12 and PHP 5.4.36.

I tried to use gdb 7.8 to gather more information. After attaching to an apache's process, I waited and finally got a segmentation fault:

(gdb) attach 205907 Attaching to process 205907 Reading symbols from /usr/local/apache2/bin/httpd...done. Reading symbols from /lib64/libpcre.so.0...(no debugging symbols found)...done. ... lots of reading symbols ... (gdb) c Continuing. Program received signal SIGSEGV, Segmentation fault. 0x00007f7508acc4fe in __longjmp () from /lib64/libc.so.6 (gdb) backtrace #0 0x00007f7508acc4fe in __longjmp () from /lib64/libc.so.6 #1 0xb7e28fbf1b781194 in ?? () Backtrace stopped: Cannot access memory at address 0xdf5a8fbf24c295cc (gdb) backtrace full #0 0x00007f7508acc4fe in __longjmp () from /lib64/libc.so.6 No symbol table info available. #1 0xb7e28fbf1b781194 in ?? () No symbol table info available. Backtrace stopped: Cannot access memory at address 0xdf5a8fbf24c295cc

Unfortunately the output is not what I expected. What should I do in order to get more information from the segmentation fault?

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  • try to enable your server core or if your process is running you can save the core with gcore command httpd.apache.org/dev/debugging.html Commented Feb 16, 2015 at 14:29

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Since you are having sig11 inside libc, and since it's not likely for it to have such easy triggering bug, I'd suggest you use a memtest86+ to test your server's memory.

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  • Worth checking, although its more likely to be a memory management bug. If memtest comes up clean, my next step would be checking all the packages are up to date, consider regressing if they are. Commented Mar 6, 2015 at 23:45
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You need the debug version of libc and probably for /lib64/libpcre.so.0...

From your output:

/lib64/libpcre.so.0...(no debugging symbols found)

I hope, that this post can be useful for you:

How to use debug version of libc

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