We have a LAMP hosting server, Nginx as frontend for static files and reverse proxy for Apache. Apache + mod_php are serving php requests.
Server Version: Apache/2.4.10 (Debian) mod_fastcgi/mod_fastcgi-SNAP-0910052141 PHP/5.6.29-0+deb8u1 Server MPM: prefork
PHP Version 5.6.29-0+deb8u1 OPCache enabled max_execution_time 60
PHP scripts dies with error Maximum execution time of 60 seconds exceeded, but apache fork is still trying to serve this requests.
Strace apache child process is empty or shows futex system call
strace -p <PID> Process <PID> attached futex(0x7f16c503890, FUTEX_WAIT_PRIVATE, 2, NULL
server status page shows that such processes are in Sending Reply or Gracefully Finishing state with a very high numbers of seconds since beginning of most recent request, beyond of Apache Timeout value.
Apache and php both are standard debian jessie main packages. Debian version is 8.7
What can be wrong and how we can change apache settings to fix these hanged forks with such long php requests.