[php-src] Issue #7931: PHP-FPM worker process stuck after slow log tracing

Issue: https://github.com/php/php-src/issues/7931 Author: midas104 ### Description Hello! I've discovered strange issue with PHP FPM worker processes. I've setup monitoring using php-fpm exporter + prometheus + grafana. There is metric called request_duration which always increases thats how I discovered that some child processes from time to time got stuck in Processing state for forever. I've attached strace and here is output ``` strace: Process 22227 attached restart_syscall(<... resuming interrupted restart_syscall ...>) ``` There were noting in dmesg or syslog, but in php-fpm log I've found that this child was stopped by FPM for tracing, so i think that this is root cause. Thanks in advance! ### PHP Version PHP 7.3.3-1+ubuntu16.04.1+deb.sury.org+1 ### Operating System Ubuntu 16.04.1