Description:
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When we use php fpm with listening on tcp port, and run other long running subprocess by proc_open, this process have also open socket for listening, after restart fpm, this socket stay listening by this process and can't start with classic "ERROR: unable to bind listening socket for address 'port number': Address already in use"

We found that problem is in missing FD_CLOEXEC flag for this socket(after dup()). 
after setting this flag, all is ok.
 
patch is below and simple and applicable for all version php.