SignalMonitor: add SignalMonitorGetEventLoop()

Eliminate the global variable "shutdown_loop".

src/SignalHandlers.cxx

@@ -25,9 +25,7 @@
 
 #include "Log.hxx"
 #include "LogInit.hxx"
-#include "Main.hxx"
 #include "event/Loop.hxx"
-#include "GlobalEvents.hxx"
 #include "system/FatalError.hxx"
 #include "util/Domain.hxx"
 
@@ -35,12 +33,10 @@
 
 static constexpr Domain signal_handlers_domain("signal_handlers");
 
-static EventLoop *shutdown_loop;
-
 static void
 HandleShutdownSignal()
 {
-	shutdown_loop->Break();
+	SignalMonitorGetEventLoop().Break();
 }
 
 static void
@@ -72,7 +68,6 @@ SignalHandlersInit(EventLoop &loop)
 	sa.sa_handler = SIG_IGN;
 	x_sigaction(SIGPIPE, &sa);
 
-	shutdown_loop = &loop;
 	SignalMonitorRegister(SIGINT, HandleShutdownSignal);
 	SignalMonitorRegister(SIGTERM, HandleShutdownSignal);
 

src/event/SignalMonitor.cxx

@@ -63,6 +63,8 @@ public:
 			SocketMonitor::Steal();
 	}
 
+	using SocketMonitor::GetEventLoop;
+
 #ifdef USE_SIGNALFD
 	void Update(sigset_t &mask) {
 		const bool was_open = SocketMonitor::IsDefined();
@@ -153,6 +155,12 @@ SignalMonitorFinish()
 	monitor.Destruct();
 }
 
+EventLoop &
+SignalMonitorGetEventLoop()
+{
+	return monitor->GetEventLoop();
+}
+
 void
 SignalMonitorRegister(int signo, SignalHandler handler)
 {

src/event/SignalMonitor.hxx

@@ -40,6 +40,13 @@ SignalMonitorInit(EventLoop &loop);
 void
 SignalMonitorFinish();
 
+/**
+ * Obtain a reference to the #EventLoop that was passed to
+ * SignalMonitorInit().
+ */
+EventLoop &
+SignalMonitorGetEventLoop();
+
 /**
  * Register a handler for the specified signal.  The handler will be
  * invoked in a safe context.