https://www.php.net/manual/it/function.pcntl-sigprocmask.php
PHP: pcntl_sigprocmask - Manual
Sets and retrieves blocked signals
phppcntlsigprocmaskmanual
https://www.openwall.com/lists/musl/2017/03/24/5
musl - Re: Re: [PATCH] Fix invalid sigprocmask call
muslpatchfixinvalidsigprocmask