Cannot run external program inside coroutine, if custom SIGHCLD handler was established

[alex-rsk]

1. Your software version (Screenshot of your startup)

   Software	Version
   PHP	8.3.13
   Swoole	5.1.4
   Laravel	10

2. Detail description about this issue(error/log)

We are running LaravelS Process, which, in turn, has been launching child processes.
As we need to watch falling of these child processes , we set custom handler for SIGCHLD in the parent process.

Child processes could call external programs (cat, touch etc). Without SIGCHLD handling in parent process, everything is working good.
But after adding SIGCHLD handler, any program cannot start.

3. Some reproducible code blocks and steps

Coroutine::set(['hook_flags' => SWOOLE_HOOK_PROC]);

run(function() {
     $this->handleSignals();
})

function handleSignals() {
    {
        $callback = function() {
            $this->close(false);
        };
        Process::signal(SIGINT, $callback);

        Process::signal(SIGTERM, $callback);

        Process::signal(SIGCHLD, function ($sig) {
            while ($ref = Process::wait(false)) {
                $message = match ($ref['pid']) {
                    $this->child1_process_pid => 'Child process 1 closed',
                    $this->child2_process_pid => 'Child process 2 closed',
                };
                $this->close(message: $message);
            }
        });
    }

Calling external program in child process:

$procResult = Process::timeout(5)->run('touch /tmp/test');
//or
$procResult = System::exec('touch /tmp/test');

Estimated result : an external program starts.

Obtained result: Program does not start. We are getting error:

Swoole\Coroutine::exec(): The signal [SIGCHLD] is registered, cannot execute swoole_coroutine_exec