SignalHandlers: move code to new class SignalMonitor

Makefile.am

@@ -296,6 +296,7 @@ libevent_a_SOURCES = \
 	src/event/EventPipe.cxx src/event/EventPipe.hxx \
 	src/event/EventFD.cxx src/event/EventFD.hxx \
 	src/event/WakeFD.hxx \
+	src/event/SignalMonitor.hxx src/event/SignalMonitor.cxx \
 	src/event/TimeoutMonitor.hxx src/event/TimeoutMonitor.cxx \
 	src/event/SocketMonitor.cxx src/event/SocketMonitor.hxx \
 	src/event/BufferedSocket.cxx src/event/BufferedSocket.hxx \

src/GlobalEvents.hxx

@@ -46,14 +46,13 @@ namespace GlobalEvents {
 		/** the current song's tag has changed */
 		TAG,
 
-		/** SIGHUP received: reload configuration, roll log file */
-		RELOAD,
-
 		/** a hardware mixer plugin has detected a change */
 		MIXER,
 
+#ifdef WIN32
 		/** shutdown requested */
 		SHUTDOWN,
+#endif
 
 		MAX
 	};

src/Main.cxx

@@ -351,6 +351,8 @@ idle_event_emitted(void)
 		state_file->CheckModified();
 }
 
+#ifdef WIN32
+
 /**
  * Handler for GlobalEvents::SHUTDOWN.
  */
@@ -360,6 +362,8 @@ shutdown_event_emitted(void)
 	main_loop->Break();
 }
 
+#endif
+
 int main(int argc, char *argv[])
 {
 #ifdef WIN32
@@ -436,7 +440,9 @@ int mpd_main(int argc, char *argv[])
 
 	GlobalEvents::Initialize();
 	GlobalEvents::Register(GlobalEvents::IDLE, idle_event_emitted);
+#ifdef WIN32
 	GlobalEvents::Register(GlobalEvents::SHUTDOWN, shutdown_event_emitted);
+#endif
 
 	Path::GlobalInit();
 
@@ -486,7 +492,7 @@ int mpd_main(int argc, char *argv[])
 
 	setup_log_output(options.log_stderr);
 
-	initSigHandlers();
+	SignalHandlersInit(*main_loop);
 
 	if (!io_thread_start(&error)) {
 		g_warning("%s", error->message);
@@ -583,6 +589,7 @@ int mpd_main(int argc, char *argv[])
 	config_global_finish();
 	stats_global_finish();
 	io_thread_deinit();
+	SignalHandlersFinish();
 	delete instance;
 	delete main_loop;
 	daemonize_finish();

src/SignalHandlers.cxx

@@ -19,6 +19,7 @@
 
 #include "config.h"
 #include "SignalHandlers.hxx"
+#include "event/SignalMonitor.hxx"
 
 #ifndef WIN32
 
@@ -32,14 +33,12 @@
 
 #include <signal.h>
 
-static void exit_signal_handler(gcc_unused int signum)
-{
-	GlobalEvents::Emit(GlobalEvents::SHUTDOWN);
-}
+static EventLoop *shutdown_loop;
 
-static void reload_signal_handler(gcc_unused int signum)
+static void
+HandleShutdownSignal()
 {
-	GlobalEvents::Emit(GlobalEvents::RELOAD);
+	shutdown_loop->Break();
 }
 
 static void
@@ -58,8 +57,11 @@ handle_reload_event(void)
 
 #endif
 
-void initSigHandlers(void)
+void
+SignalHandlersInit(EventLoop &loop)
 {
+	SignalMonitorInit(loop);
+
 #ifndef WIN32
 	struct sigaction sa;
 
@@ -68,12 +70,16 @@ void initSigHandlers(void)
 	sa.sa_handler = SIG_IGN;
 	x_sigaction(SIGPIPE, &sa);
 
-	sa.sa_handler = exit_signal_handler;
-	x_sigaction(SIGINT, &sa);
-	x_sigaction(SIGTERM, &sa);
+	shutdown_loop = &loop;
+	SignalMonitorRegister(SIGINT, HandleShutdownSignal);
+	SignalMonitorRegister(SIGTERM, HandleShutdownSignal);
 
-	GlobalEvents::Register(GlobalEvents::RELOAD, handle_reload_event);
-	sa.sa_handler = reload_signal_handler;
-	x_sigaction(SIGHUP, &sa);
+	SignalMonitorRegister(SIGHUP, handle_reload_event);
 #endif
 }
+
+void
+SignalHandlersFinish()
+{
+	SignalMonitorFinish();
+}

src/SignalHandlers.hxx

@@ -20,6 +20,12 @@
 #ifndef MPD_SIGNAL_HANDLERS_HXX
 #define MPD_SIGNAL_HANDLERS_HXX
 
-void initSigHandlers(void);
+class EventLoop;
+
+void
+SignalHandlersInit(EventLoop &loop);
+
+void
+SignalHandlersFinish();
 
 #endif

src/event/SignalMonitor.cxx

+/*
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "SignalMonitor.hxx"
+
+#ifndef WIN32
+
+#include "WakeFD.hxx"
+#include "SocketMonitor.hxx"
+#include "util/Manual.hxx"
+#include "system/FatalError.hxx"
+
+#include <atomic>
+#include <algorithm>
+
+class SignalMonitor final : private SocketMonitor {
+	WakeFD fd;
+
+public:
+	SignalMonitor(EventLoop &_loop)
+		:SocketMonitor(_loop) {
+		SocketMonitor::Open(fd.Get());
+		SocketMonitor::ScheduleRead();
+	}
+
+	~SignalMonitor() {
+		/* prevent the descriptor to be closed twice */
+		SocketMonitor::Steal();
+	}
+
+	void WakeUp() {
+		fd.Write();
+	}
+
+private:
+	virtual bool OnSocketReady(unsigned flags) override;
+};
+
+/* this should be enough - is it? */
+static constexpr unsigned MAX_SIGNAL = 64;
+
+static SignalHandler signal_handlers[MAX_SIGNAL];
+static std::atomic_bool signal_pending[MAX_SIGNAL];
+
+static Manual<SignalMonitor> monitor;
+
+static void
+SignalCallback(int signo)
+{
+	assert(signal_handlers[signo] != nullptr);
+
+	if (!signal_pending[signo].exchange(true))
+		monitor->WakeUp();
+}
+
+void
+SignalMonitorInit(EventLoop &loop)
+{
+	monitor.Construct(loop);
+}
+
+static void
+x_sigaction(int signum, const struct sigaction &act)
+{
+	if (sigaction(signum, &act, nullptr) < 0)
+		FatalSystemError("sigaction() failed");
+}
+
+void
+SignalMonitorFinish()
+{
+	struct sigaction sa;
+	sa.sa_flags = 0;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_handler = SIG_DFL;
+
+	for (unsigned i = 0; i < MAX_SIGNAL; ++i) {
+		if (signal_handlers[i] != nullptr) {
+			x_sigaction(i, sa);
+			signal_handlers[i] = nullptr;
+		}
+	}
+
+	std::fill_n(signal_pending, MAX_SIGNAL, false);
+
+	monitor.Destruct();
+}
+
+void
+SignalMonitorRegister(int signo, SignalHandler handler)
+{
+	assert(signal_handlers[signo] == nullptr);
+	assert(!signal_pending[signo]);
+
+	signal_handlers[signo] = handler;
+
+	struct sigaction sa;
+	sa.sa_flags = 0;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_handler = SignalCallback;
+	x_sigaction(signo, sa);
+}
+
+bool
+SignalMonitor::OnSocketReady(unsigned)
+{
+	fd.Read();
+
+	for (unsigned i = 0; i < MAX_SIGNAL; ++i)
+		if (signal_pending[i].exchange(false))
+			signal_handlers[i]();
+
+	return true;
+}
+
+#endif

src/event/SignalMonitor.hxx

+/*
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_SOCKET_SIGNAL_MONITOR_HXX
+#define MPD_SOCKET_SIGNAL_MONITOR_HXX
+
+#include "check.h"
+
+class EventLoop;
+
+#ifndef WIN32
+
+typedef void (*SignalHandler)();
+
+/**
+ * Initialise the signal monitor subsystem.
+ */
+void
+SignalMonitorInit(EventLoop &loop);
+
+/**
+ * Deinitialise the signal monitor subsystem.
+ */
+void
+SignalMonitorFinish();
+
+/**
+ * Register a handler for the specified signal.  The handler will be
+ * invoked in a safe context.
+ */
+void
+SignalMonitorRegister(int signo, SignalHandler handler);
+
+#else
+
+static inline void
+SignalMonitorInit(EventLoop &)
+{
+}
+
+static inline void
+SignalMonitorFinish()
+{
+}
+
+#endif
+
+#endif /* MAIN_NOTIFY_H */