Description:
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I am seeing random SIGSEGV and SIGABRT among a # of different fpm-pools in both 5.5.19 and 5.5.20.  This behavior was not seen with 5.5.18.

Test script:
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This is happening in 100s of different sites all running the wordpress 4.0.1 though with different plugins/themes.  I haven't been able to detect the code causing the problem since it only shows up randomly under load.



Actual result:
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#0  0x00007f5c129253c4 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0  0x00007f5c129253c4 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
#1  0x0000000000791dfe in fpm_children_free (child=<optimized out>)
    at /build/buildd/php5-5.5.20+dfsg/sapi/fpm/fpm/fpm_children.c:170
#2  0x000000000079ffcd in fpm_worker_pool_cleanup (which=<optimized out>, arg=<optimized out>)
    at /build/buildd/php5-5.5.20+dfsg/sapi/fpm/fpm/fpm_worker_pool.c:43
#3  0x00000000007928e6 in fpm_cleanups_run (type=1)
    at /build/buildd/php5-5.5.20+dfsg/sapi/fpm/fpm/fpm_cleanup.c:45
#4  0x0000000000791d21 in fpm_run (max_requests=0x7ffff25cd1e8)
    at /build/buildd/php5-5.5.20+dfsg/sapi/fpm/fpm/fpm.c:117
#5  0x0000000000466408 in main (argc=6, argv=0x7ffff25cf358)
    at /build/buildd/php5-5.5.20+dfsg/sapi/fpm/fpm/fpm_main.c:1862