Unify 'Signal_dispatcher' interfaces

Several users of the signal API used custom convenience classes to
invoke signal-handling functions on the reception of incoming signals.
The 'Signal_dispatcher' pattern turned out to be particularly useful. To
avoid the duplication of this code across the code base, this patch
adds the interface to 'base/signal.h'.

Furthermore, the patch changes the 'Signal::num()' return type from int
to unsigned because negative numbers are meaningless here.

Fixes #511

base/include/base/signal.h

@@ -52,7 +52,7 @@ namespace Genode {
 			friend class Signal_context;
 
 			Signal_context *_context;
-			int             _num;
+			unsigned        _num;
 
 			/**
 			 * Constructor
@@ -63,7 +63,7 @@ namespace Genode {
 			 *
 			 * Signal objects are constructed only by signal receivers.
 			 */
-			Signal(Signal_context *context, int num)
+			Signal(Signal_context *context, unsigned num)
 			: _context(context), _num(num)
 			{ }
 
@@ -82,7 +82,7 @@ namespace Genode {
 			/**
 			 * Return number of signals received from the same transmitter
 			 */
-			int num() { return _num; }
+			unsigned num() const { return _num; }
 	};
 
 	/**
@@ -191,7 +191,7 @@ namespace Genode {
 			 *
 			 * \param cnt  number of signals to submit at once
 			 */
-			void submit(int cnt = 1);
+			void submit(unsigned cnt = 1);
 	};
 
 
@@ -282,6 +282,61 @@ namespace Genode {
 			 */
 			static void dispatch_signals(Signal_source *signal_source);
 	};
+
+
+	/**
+	 * Abstract interface to be implemented by signal dispatchers
+	 */
+	struct Signal_dispatcher_base : Signal_context
+	{
+		virtual void dispatch(unsigned num) = 0;
+	};
+
+
+	/**
+	 * Adapter for directing signals to member functions
+	 *
+	 * This utility associates member functions with signals. It is intended to
+	 * be used as a member variable of the class that handles incoming signals
+	 * of a certain type. The constructor takes a pointer-to-member to the
+	 * signal handling function as argument. If a signal is received at the
+	 * common signal reception code, this function will be invoked by calling
+	 * 'Signal_dispatcher_base::dispatch'.
+	 *
+	 * \param T  type of signal-handling class
+	 */
+	template <typename T>
+	class Signal_dispatcher : private Signal_dispatcher_base,
+	                          public  Signal_context_capability
+	{
+		private:
+
+			T &obj;
+			void (T::*member) (unsigned);
+			Signal_receiver &sig_rec;
+
+		public:
+
+			/**
+			 * Constructor
+			 *
+			 * \param sig_rec     signal receiver to associate the signal
+			 *                    handler with
+			 * \param obj,member  object and member function to call when
+			 *                    the signal occurs
+			 */
+			Signal_dispatcher(Signal_receiver &sig_rec,
+			                  T &obj, void (T::*member)(unsigned))
+			:
+				Signal_context_capability(sig_rec.manage(this)),
+				obj(obj), member(member),
+				sig_rec(sig_rec)
+			{ }
+
+			~Signal_dispatcher() { sig_rec.dissolve(this); }
+
+			void dispatch(unsigned num) { (obj.*member)(num); }
+	};
 }
 
 #endif /* _INCLUDE__BASE__SIGNAL_H__ */

base/src/base/signal/signal.cc

@@ -179,7 +179,7 @@ void Signal_transmitter::context(Signal_context_capability context)
 }
 
 
-void Signal_transmitter::submit(int cnt)
+void Signal_transmitter::submit(unsigned cnt)
 {
 	signal_connection()->submit(_context, cnt);
 }
@@ -347,7 +347,7 @@ void Signal_receiver::local_submit(Signal ns)
 	 * counters. In the common case, the current signal is an invalid
 	 * signal with a counter value of zero.
 	 */
-	int num = context->_curr_signal.num() + ns.num();
+	unsigned num = context->_curr_signal.num() + ns.num();
 	context->_curr_signal = Signal(context, num);
 
 	/* wake up the receiver if the context becomes pending */

base/src/test/rm_nested/main.cc

@@ -75,8 +75,8 @@ class Local_fault_handler : public Thread<4096>
 			while (true) {
 				printf("fault handler: waiting for fault signal\n");
 				Signal signal = _receiver->wait_for_signal();
-				printf("received %d fault signals\n", signal.num());
+				printf("received %u fault signals\n", signal.num());
-				for (int i = 0; i < signal.num(); i++)
+				for (unsigned i = 0; i < signal.num(); i++)
 					handle_fault();
 			}
 		}

dde_linux/src/drivers/usb/nic/component.h

@@ -128,7 +128,7 @@ namespace Nic {
 
 		protected:
 
-			void _process_packets()
+			void _process_packets(unsigned)
 			{
 				static sk_buff work_skb; /* dummy skb for fixup calls */
 				static Counter counter("TX");

dde_linux/src/drivers/usb/signal/dispatch.h

@@ -17,40 +17,6 @@
 
 #include "signal.h"
 
-template <typename T>
-class Signal_dispatcher : public Driver_context,
-                          public Genode::Signal_context_capability
-{
-	private:
-
-		T &obj;
-		void (T::*member) ();
-		Genode::Signal_receiver *sig_rec;
-
-	public:
-
-		/**
-		 * Constructor
-		 *
-		 * \param sig_rec     signal receiver to associate the signal
-		 *                    handler with
-		 * \param obj,member  object and member function to call when
-		 *                    the signal occurs
-		 */
-		Signal_dispatcher(Genode::Signal_receiver *sig_rec,
-		                  T &obj, void (T::*member)())
-		:
-			Genode::Signal_context_capability(sig_rec->manage(this)),
-			obj(obj), member(member),
-			sig_rec(sig_rec)
-		{ }
-
-		~Signal_dispatcher() { sig_rec->dissolve(this); }
-
-		void handle() { (obj.*member)(); }
-		char const *debug() { return "Signal_dispatcher"; }
-};
-
 
 /**
  * Session components that overrides signal handlers
@@ -60,11 +26,11 @@ class Packet_session_component : public RPC
 {
 	private:
 
-		Signal_dispatcher<Packet_session_component> _process_packet_dispatcher;
+		Genode::Signal_dispatcher<Packet_session_component> _process_packet_dispatcher;
 
 	protected:
 
-		virtual void _process_packets() = 0;
+		virtual void _process_packets(unsigned) = 0;
 
 	public:
 
@@ -73,7 +39,7 @@ class Packet_session_component : public RPC
 		                         Genode::Signal_receiver      *sig_rec)
 		:
 			RPC(tx_ds, ep),
-			_process_packet_dispatcher(sig_rec, *this,
+			_process_packet_dispatcher(*sig_rec, *this,
 			                           &Packet_session_component::_process_packets)
 		{ 
 			/*
@@ -91,7 +57,7 @@ class Packet_session_component : public RPC
 		                         Genode::Signal_receiver      *sig_rec)
 		:
 			RPC(tx_ds, rx_ds, rx_buffer_alloc, ep),
-			_process_packet_dispatcher(sig_rec, *this,
+			_process_packet_dispatcher(*sig_rec, *this,
 			                           &Packet_session_component::_process_packets)
 		{ 
 			/*

dde_linux/src/drivers/usb/storage/component.h

@@ -51,7 +51,7 @@ namespace Block {
 
 		protected:
 
-			void _process_packets()
+			void _process_packets(unsigned)
 			{
 				while (tx_sink()->packet_avail())
 				{

dde_oss/src/drivers/oss/main.cc

@@ -31,46 +31,6 @@ static const bool verbose = false;
 static bool audio_out_active = false;
 
 
-/**
- * Packet-stream signal dispatcher
- *
- * TODO: Move to generic code
- */
-template <typename T>
-class Signal_dispatcher : public Driver_context,
-                          public Genode::Signal_context_capability
-{
-	private:
-
-		T &obj;
-		void (T::*member) ();
-		Genode::Signal_receiver *sig_rec;
-
-	public:
-
-		/**
-		 * Constructor
-		 *
-		 * \param sig_rec     signal receiver to associate the signal
-		 *                    handler with
-		 * \param obj,member  object and member function to call when
-		 *                    the signal occurs
-		 */
-		Signal_dispatcher(Genode::Signal_receiver *sig_rec,
-		                  T &obj, void (T::*member)())
-		:
-			Genode::Signal_context_capability(sig_rec->manage(this)),
-			obj(obj), member(member),
-			sig_rec(sig_rec)
-		{ }
-
-		~Signal_dispatcher() { sig_rec->dissolve(this); }
-
-		void handle() { (obj.*member)(); }
-		char const *debug() { return "Signal_dispatcher"; }
-};
-
-
 namespace Audio_out {
 
 	class Session_component;
@@ -94,7 +54,7 @@ namespace Audio_out {
 				return _ds;
 			}
 
-			void _process_packets()
+			void _process_packets(unsigned)
 			{
 				/* handle audio-out packets */
 				Session_component *left  = channel_acquired[LEFT],
@@ -137,7 +97,7 @@ namespace Audio_out {
 		public:
 
 			Session_component(Channel_number channel, size_t buffer_size,
-			                  Rpc_entrypoint &ep, Signal_receiver *sig_rec)
+			                  Rpc_entrypoint &ep, Signal_receiver &sig_rec)
 			: Session_rpc_object(_alloc_dataspace(buffer_size), ep), _channel(channel),
 			  _process_packet_dispatcher(sig_rec, *this,
 			                             &Session_component::_process_packets)
@@ -233,7 +193,7 @@ namespace Audio_out {
 		private:
 
 			Rpc_entrypoint  &_channel_ep;
-			Signal_receiver *_sig_rec;
+			Signal_receiver &_sig_rec;
 
 		protected:
 
@@ -258,8 +218,8 @@ namespace Audio_out {
 
 		public:
 
-			Root(Rpc_entrypoint *session_ep, Allocator *md_alloc, Signal_receiver *sig_rec)
+			Root(Rpc_entrypoint &session_ep, Allocator *md_alloc, Signal_receiver &sig_rec)
-			: Root_component(session_ep, md_alloc), _channel_ep(*session_ep), _sig_rec(sig_rec)
+			: Root_component(&session_ep, md_alloc), _channel_ep(session_ep), _sig_rec(sig_rec)
 			{ }
 	};
 }
@@ -282,7 +242,7 @@ int main()
 	audio_out_active = audio_init() ? false : true;
 
 	if (audio_out_active) {
-		static Audio_out::Root audio_root(&ep, env()->heap(), &recv);
+		static Audio_out::Root audio_root(ep, env()->heap(), recv);
 		env()->parent()->announce(ep.manage(&audio_root));
 	}
 

libports/src/server/ffat_fs/main.cc

@@ -49,53 +49,6 @@ static bool const verbose = false;
 #define PDBGV(...) if (verbose) PDBG(__VA_ARGS__)
 
 
-/*************************************
- ** Helpers for dispatching signals **
- *************************************/
-
-namespace Genode {
-
-	struct Signal_dispatcher_base : Signal_context
-	{
-		virtual void dispatch(int num) = 0;
-	};
-
-
-	template <typename T>
-	class Signal_dispatcher : private Signal_dispatcher_base,
-	                          public  Signal_context_capability
-	{
-		private:
-
-			T &obj;
-			void (T::*member) (int);
-			Signal_receiver &sig_rec;
-
-		public:
-
-			/**
-			 * Constructor
-			 *
-			 * \param sig_rec     signal receiver to associate the signal
-			 *                    handler with
-			 * \param obj,member  object and member function to call when
-			 *                    the signal occurs
-			 */
-			Signal_dispatcher(Signal_receiver &sig_rec,
-			                  T &obj, void (T::*member)(int))
-			:
-				Signal_context_capability(sig_rec.manage(this)),
-				obj(obj), member(member),
-				sig_rec(sig_rec)
-			{ }
-
-			~Signal_dispatcher() { sig_rec.dissolve(this); }
-
-			void dispatch(int num) { (obj.*member)(num); }
-	};
-}
-
-
 /*************************
  ** File-system service **
  *************************/
@@ -180,7 +133,7 @@ namespace File_system {
 			 * Called by signal dispatcher, executed in the context of the main
 			 * thread (not serialized with the RPC functions)
 			 */
-			void _process_packets(int)
+			void _process_packets(unsigned)
 			{
 				while (tx_sink()->packet_avail()) {
 
@@ -255,7 +208,7 @@ namespace File_system {
 			                 Mode mode, bool create)
 			{
 				PDBGV("_root = %s, dir_name = %s, name = %s, create = %d",
- 				      _root.name(),
+				      _root.name(),
 				      _handle_registry.lookup(dir_handle)->name(),
 				      name.string(),
 				      create);

os/src/server/iso9660/main.cc

@@ -225,7 +225,7 @@ namespace Iso {
 					try {
 						Signal signal = _receiver.wait_for_signal();
 
-						for (int i = 0; i < signal.num(); i++)
+						for (unsigned i = 0; i < signal.num(); i++)
 							static_cast<File *>(signal.context())->handle_fault();
 					} catch (...) {
 						PDBG("unexpected error while waiting for signal");

os/src/server/ram_fs/main.cc

@@ -26,53 +26,6 @@
 #include <node_handle_registry.h>
 
 
-/*************************************
- ** Helpers for dispatching signals **
- *************************************/
-
-namespace Genode {
-
-	struct Signal_dispatcher_base : Signal_context
-	{
-		virtual void dispatch(int num) = 0;
-	};
-
-
-	template <typename T>
-	class Signal_dispatcher : private Signal_dispatcher_base,
-	                          public  Signal_context_capability
-	{
-		private:
-
-			T &obj;
-			void (T::*member) (int);
-			Signal_receiver &sig_rec;
-
-		public:
-
-			/**
-			 * Constructor
-			 *
-			 * \param sig_rec     signal receiver to associate the signal
-			 *                    handler with
-			 * \param obj,member  object and member function to call when
-			 *                    the signal occurs
-			 */
-			Signal_dispatcher(Signal_receiver &sig_rec,
-			                  T &obj, void (T::*member)(int))
-			:
-				Signal_context_capability(sig_rec.manage(this)),
-				obj(obj), member(member),
-				sig_rec(sig_rec)
-			{ }
-
-			~Signal_dispatcher() { sig_rec.dissolve(this); }
-
-			void dispatch(int num) { (obj.*member)(num); }
-	};
-}
-
-
 /*************************
  ** File-system service **
  *************************/
@@ -155,7 +108,7 @@ namespace File_system {
 			 * Called by signal dispatcher, executed in the context of the main
 			 * thread (not serialized with the RPC functions)
 			 */
-			void _process_packets(int)
+			void _process_packets(unsigned)
 			{
 				while (tx_sink()->packet_avail()) {
 

os/src/server/tar_fs/main.cc

@@ -36,53 +36,6 @@ static bool const verbose = false;
 #define PDBGV(...) if (verbose) PDBG(__VA_ARGS__)
 
 
-/*************************************
- ** Helpers for dispatching signals **
- *************************************/
-
-namespace Genode {
-
-	struct Signal_dispatcher_base : Signal_context
-	{
-		virtual void dispatch(int num) = 0;
-	};
-
-
-	template <typename T>
-	class Signal_dispatcher : private Signal_dispatcher_base,
-	                          public  Signal_context_capability
-	{
-		private:
-
-			T &obj;
-			void (T::*member) (int);
-			Signal_receiver &sig_rec;
-
-		public:
-
-			/**
-			 * Constructor
-			 *
-			 * \param sig_rec     signal receiver to associate the signal
-			 *                    handler with
-			 * \param obj,member  object and member function to call when
-			 *                    the signal occurs
-			 */
-			Signal_dispatcher(Signal_receiver &sig_rec,
-			                  T &obj, void (T::*member)(int))
-			:
-				Signal_context_capability(sig_rec.manage(this)),
-				obj(obj), member(member),
-				sig_rec(sig_rec)
-			{ }
-
-			~Signal_dispatcher() { sig_rec.dissolve(this); }
-
-			void dispatch(int num) { (obj.*member)(num); }
-	};
-}
-
-
 /*************************
  ** File-system service **
  *************************/
@@ -167,7 +120,7 @@ namespace File_system {
 			 * Called by signal dispatcher, executed in the context of the main
 			 * thread (not serialized with the RPC functions)
 			 */
-			void _process_packets(int)
+			void _process_packets(unsigned)
 			{
 				while (tx_sink()->packet_avail()) {
 
@@ -241,7 +194,7 @@ namespace File_system {
 			                 Mode mode, bool create)
 			{
 				PDBGV("_root = %s, dir_name = %s, name = %s, create = %d",
- 				      _root.record()->name(),
+				      _root.record()->name(),
 				      _handle_registry.lookup(dir_handle)->record()->name(),
 				      name.string(),
 				      create);

os/src/test/dynamic_config/main.cc

@@ -32,31 +32,22 @@ int main(int, char **)
 {
 	parse_config();
 
-	struct Signal_dispatcher : public Genode::Signal_context
-	{
-		void dispatch()
-		{
-			try {
-				Genode::config()->reload();
-				parse_config();
-			} catch (Genode::Config::Invalid) {
-				PERR("Error: reloading config failed");
-			}
-		}
-	} signal_dispatcher;
-
-	static Genode::Signal_receiver sig_rec;
-
 	/* register signal handler for config changes */
-	Genode::config()->sigh(sig_rec.manage(&signal_dispatcher));
+	Genode::Signal_receiver sig_rec;
+	Genode::Signal_context sig_ctx;
+	Genode::config()->sigh(sig_rec.manage(&sig_ctx));
 
 	for (;;) {
 
 		/* wait for config change */
-		Genode::Signal signal = sig_rec.wait_for_signal();
+		sig_rec.wait_for_signal();
 
-		for (int i = 0; i < signal.num(); i++)
+		try {
-			static_cast<Signal_dispatcher *>(signal.context())->dispatch();
+			Genode::config()->reload();
+			parse_config();
+		} catch (Genode::Config::Invalid) {
+			PERR("Error: reloading config failed");
+		}
 	}
 	return 0;
 }

os/src/test/iso/main.cc

@@ -55,7 +55,7 @@ class Pager : public Thread<8192>
 			while (true) {
 				Signal signal = _receiver.wait_for_signal();
 
-				for (int i = 0; i < signal.num(); i++)
+				for (unsigned i = 0; i < signal.num(); i++)
 					handle_fault();
 			}
 		}

os/src/test/signal/main.cc

@@ -133,7 +133,7 @@ class Handler : Thread<4096>
 					Signal signal = _receiver->wait_for_signal();
 
 					if (_verbose)
-						printf("handler %d got %d signal%s with context %p\n",
+						printf("handler %d got %u signal%s with context %p\n",
 						       _id,
 						       signal.num(),
 						       signal.num() == 1 ? "" : "s",
@@ -191,12 +191,12 @@ class Handler : Thread<4096>
 		/**
 		 * Return total number of received notifications
 		 */
-		unsigned receive_cnt() { return _receive_cnt; }
+		unsigned receive_cnt() const { return _receive_cnt; }
 
 		/**
 		 * Return total number of signal-handler activations
 		 */
-		unsigned activation_cnt() { return _activation_cnt; }
+		unsigned activation_cnt() const { return _activation_cnt; }
 };
 
 
@@ -242,7 +242,7 @@ class Id_signal_context : public Signal_context
 
 		Id_signal_context(int id) : _id(id) { }
 
-		int id() { return _id; }
+		int id() const { return _id; }
 };
 
 

ports/src/noux/child.h

@@ -23,7 +23,6 @@
 /* Noux includes */
 #include <file_descriptor_registry.h>
 #include <dir_file_system.h>
-#include <signal_dispatcher.h>
 #include <noux_session/capability.h>
 #include <args.h>
 #include <environment.h>
@@ -88,7 +87,7 @@ namespace Noux {
 	/**
 	 * Signal context used for child exit
 	 */
-	class Child_exit_dispatcher : public Signal_dispatcher
+	class Child_exit_dispatcher : public Signal_dispatcher_base
 	{
 		private:
 
@@ -98,7 +97,7 @@ namespace Noux {
 
 			Child_exit_dispatcher(Child *child) : _child(child) { }
 
-			void dispatch()
+			void dispatch(unsigned)
 			{
 				if (is_init_process(_child)) {
 					PINF("init process exited");
@@ -121,7 +120,7 @@ namespace Noux {
 	/**
 	 * Signal context used for removing the child after having executed 'execve'
 	 */
-	class Child_execve_cleanup_dispatcher : public Signal_dispatcher
+	class Child_execve_cleanup_dispatcher : public Signal_dispatcher_base
 	{
 		private:
 
@@ -131,7 +130,7 @@ namespace Noux {
 
 			Child_execve_cleanup_dispatcher(Child *child) : _child(child) { }
 
-			void dispatch()
+			void dispatch(unsigned)
 			{
 				destroy(env()->heap(), _child);
 			}

ports/src/noux/main.cc

@@ -897,11 +897,11 @@ int main(int argc, char **argv)
 
 		Genode::Signal signal = sig_rec.wait_for_signal();
 
-		Signal_dispatcher *dispatcher =
+		Signal_dispatcher_base *dispatcher =
-			static_cast<Signal_dispatcher *>(signal.context());
+			static_cast<Signal_dispatcher_base *>(signal.context());
 
-		for (int i = 0; i < signal.num(); i++)
+		for (unsigned i = 0; i < signal.num(); i++)
-			dispatcher->dispatch();
+			dispatcher->dispatch(1);
 	}
 
 	PINF("-- exiting noux ---");

ports/src/noux/pipe_io_channel.h

@@ -207,7 +207,7 @@ namespace Noux {
 	};
 
 
-	class Pipe_sink_io_channel : public Io_channel, public Signal_dispatcher
+	class Pipe_sink_io_channel : public Io_channel, public Signal_dispatcher_base
 	{
 		private:
 
@@ -258,21 +258,21 @@ namespace Noux {
 				return true;
 			}
 
-			/*********************************
+			/**************************************
-			 ** Signal_dispatcher interface **
+			 ** Signal_dispatcher_base interface **
-			 *********************************/
+			 **************************************/
 
 			/**
 			 * Called by Noux main loop on the occurrence of new STDIN input
 			 */
-			void dispatch()
+			void dispatch(unsigned)
 			{
 				Io_channel::invoke_all_notifiers();
 			}
 	};
 
 
-	class Pipe_source_io_channel : public Io_channel, public Signal_dispatcher
+	class Pipe_source_io_channel : public Io_channel, public Signal_dispatcher_base
 	{
 		private:
 
@@ -320,14 +320,14 @@ namespace Noux {
 				return true;
 			}
 
-			/*********************************
+			/**************************************
-			 ** Signal_dispatcher interface **
+			 ** Signal_dispatcher_base interface **
-			 *********************************/
+			 **************************************/
 
 			/**
 			 * Called by Noux main loop on the occurrence of new STDIN input
 			 */
-			void dispatch()
+			void dispatch(unsigned)
 			{
 				Io_channel::invoke_all_notifiers();
 			}

ports/src/noux/signal_dispatcher.h

@@ -1,28 +0,0 @@
-/*
- * \brief  Abstract interface for dispatching signals
- * \author Norman Feske
- * \date   2011-02-17
- */
-
-/*
- * Copyright (C) 2011-2012 Genode Labs GmbH
- *
- * This file is part of the Genode OS framework, which is distributed
- * under the terms of the GNU General Public License version 2.
- */
-
-#ifndef _NOUX__SIGNAL_DISPATCHER_H_
-#define _NOUX__SIGNAL_DISPATCHER_H_
-
-/* Genode includes */
-#include <base/signal.h>
-
-namespace Noux {
-
-	struct Signal_dispatcher : public Signal_context
-	{
-		virtual void dispatch() = 0;
-	};
-}
-
-#endif /* _NOUX__SIGNAL_DISPATCHER_H_ */

ports/src/noux/terminal_io_channel.h

@@ -25,7 +25,7 @@
 
 namespace Noux {
 
-	struct Terminal_io_channel : Io_channel, Signal_dispatcher
+	struct Terminal_io_channel : Io_channel, Signal_dispatcher_base
 	{
 		Terminal::Session &terminal;
 		Signal_receiver   &sig_rec;
@@ -185,14 +185,14 @@ namespace Noux {
 		}
 
 
-		/*********************************
+		/**************************************
-		 ** Signal_dispatcher interface **
+		 ** Signal_dispatcher_base interface **
-		 *********************************/
+		 **************************************/
 
 		/**
 		 * Called by Noux main loop on the occurrence of new STDIN input
 		 */
-		void dispatch()
+		void dispatch(unsigned)
 		{
 			Io_channel::invoke_all_notifiers();
 		}