LibCore: Add 'notify_forked()' to tear down the eventloop in forked c…

…hild

This makes the forked process capable of constructing a new event loop,
should it choose to.

Libraries/LibCore/EventLoop.cpp

@@ -519,6 +519,26 @@ void EventLoop::unregister_signal(int handler_id)
  s_signal_handlers.remove(remove_signo);
 }
 
+void EventLoop::notify_forked(ForkEvent event)
+{
+ switch (event) {
+ case ForkEvent::Child:
+ s_main_event_loop = nullptr;
+ s_event_loop_stack->clear();
+ s_timers->clear();
+ s_notifiers->clear();
+ s_signal_handlers.clear();
+ s_handling_signal = 0;
+ s_next_signal_id = 0;
+ s_pid = 0;
+ s_rpc_server = nullptr;
+ s_rpc_clients.clear();
+ return;
+ }
+
+ ASSERT_NOT_REACHED();
+}
+
 void EventLoop::wait_for_event(WaitMode mode)
 {
  fd_set rfds;

Libraries/LibCore/EventLoop.h

@@ -81,6 +81,13 @@ class EventLoop {
  static int register_signal(int signo, Function<void(int)> handler);
  static void unregister_signal(int handler_id);
 
+ // Note: Boost uses Parent/Child/Prepare, but we don't really have anything
+ // interesting to do in the parent or before forking.
+ enum class ForkEvent {
+ Child,
+ };
+ static void notify_forked(ForkEvent);
+
 private:
  bool start_rpc_server();
  void wait_for_event(WaitMode);
@@ -102,8 +109,8 @@ class EventLoop {
 
  class SignalHandlers {
  AK_MAKE_NONCOPYABLE(SignalHandlers);
- public:
 
+ public:
  SignalHandlers(SignalHandlers&& from)
  : m_signo(from.m_signo)
  , m_original_handler(from.m_original_handler)