base: don't throw exceptions in 'Signal_receiver::pending_signal()'

Issue #3922

repos/base-hw/src/lib/base/signal_receiver.cc

@@ -158,7 +158,7 @@ Signal Signal_receiver::pending_signal()
 	Signal::Data result;
 	_contexts.for_each_locked([&] (Signal_context &context) {
 
-		if (!context._pending) return;
+		if (!context._pending) return false;
 
 		_contexts.head(context._next);
 		context._pending     = false;
@@ -166,7 +166,7 @@ Signal Signal_receiver::pending_signal()
 		context._curr_signal = Signal::Data(0, 0);
 
 		Trace::Signal_received trace_event(context, result.num);
-		throw Context_ring::Break_for_each();
+		return true;
 	});
 	if (result.context) {
 		Mutex::Guard context_guard(result.context->_mutex);
@@ -178,7 +178,7 @@ Signal Signal_receiver::pending_signal()
 
 	/* look for pending signals */
 	if (Kernel::pending_signal(Capability_space::capid(_cap)) != 0) {
-		throw Signal_not_pending();
+		return Signal();
 	}
 
 	/* read signal data */

repos/base/include/base/signal.h

@@ -88,7 +88,12 @@ class Genode::Signal
 			 */
 			Data() : context(0), num(0) { }
 
-		} _data;
+		} _data { };
+
+		/**
+		 * Constructor for invalid signal
+		 */
+		Signal() { };
 
 		/**
 		 * Constructor
@@ -117,6 +122,7 @@ class Genode::Signal
 
 		Signal_context *context()       { return _data.context; }
 		unsigned        num()     const { return _data.num; }
+		bool            valid()   const { return _data.context != nullptr; }
 };
 
 
@@ -299,9 +305,7 @@ class Genode::Signal_receiver : Noncopyable
 
 					do {
 						Mutex::Guard mutex_guard(context->_mutex);
-						try {
-							functor(*context);
-						} catch (Break_for_each) { return; }
+						if (functor(*context)) return;
 						context = context->_next;
 					} while (context != _head);
 				}
@@ -352,7 +356,6 @@ class Genode::Signal_receiver : Noncopyable
 		 */
 		class Context_already_in_use { };
 		class Context_not_associated { };
-		class Signal_not_pending     { };
 
 		/**
 		 * Constructor
@@ -403,8 +406,7 @@ class Genode::Signal_receiver : Noncopyable
 		/**
 		 * Retrieve pending signal
 		 *
-		 * \throw   'Signal_not_pending' no pending signal found
-		 * \return  received signal
+		 * \return  received signal (invalid if no pending signal found)
 		 */
 		Signal pending_signal();
 

repos/base/src/core/signal_receiver.cc

@@ -50,6 +50,6 @@ void Signal_receiver::block_for_signal()
 }
 
 Signal Signal_receiver::pending_signal() {
-	throw Signal_not_pending(); }
+	return Signal(); }
 
 void Signal_receiver::local_submit(Signal::Data) { ASSERT_NEVER_CALLED; }

repos/base/src/lib/base/entrypoint.cc

@@ -55,15 +55,17 @@ void Entrypoint::Signal_proxy_component::signal()
 	 * Note, we handle only one signal here to ensure fairness between RPCs and
 	 * signals.
 	 */
-	try {
+
 	Signal sig = ep._sig_rec->pending_signal();
+
+	if (sig.valid()) {
 		ep._dispatch_signal(sig);
 
 		if (sig.context()->level() == Signal_context::Level::Io) {
 			/* trigger the progress handler */
 			io_progress = true;
 		}
-	} catch (Signal_receiver::Signal_not_pending) { }
+	}
 
 	if (io_progress)
 		ep._handle_io_progress();
@@ -185,9 +187,10 @@ bool Entrypoint::_wait_and_dispatch_one_io_signal(bool const dont_block)
 
 	for (;;) {
 
-		try {
 		Signal sig = _sig_rec->pending_signal();
 
+		if (sig.valid()) {
+
 			/* defer application-level signals */
 			if (sig.context()->level() == Signal_context::Level::App) {
 				_defer_signal(sig);
@@ -196,8 +199,8 @@ bool Entrypoint::_wait_and_dispatch_one_io_signal(bool const dont_block)
 
 			_dispatch_signal(sig);
 			break;
+		}
 
-		} catch (Signal_receiver::Signal_not_pending) {
 		if (dont_block)
 			return false;
 
@@ -231,7 +234,6 @@ bool Entrypoint::_wait_and_dispatch_one_io_signal(bool const dont_block)
 				_sig_rec->block_for_signal();
 		}
 	}
-	}
 
 	/* initiate potential deferred-signal handling in entrypoint */
 	if (_deferred_signals.first()) {

repos/base/src/lib/base/signal.cc

@@ -235,13 +235,14 @@ void Signal_receiver::block_for_signal()
 	_signal_available.down();
 }
 
+
 Signal Signal_receiver::pending_signal()
 {
 	Mutex::Guard contexts_guard(_contexts_mutex);
 	Signal::Data result;
-	_contexts.for_each_locked([&] (Signal_context &context) {
+	_contexts.for_each_locked([&] (Signal_context &context) -> bool {
 
-		if (!context._pending) return;
+		if (!context._pending) return false;
 
 		_contexts.head(context._next);
 		context._pending     = false;
@@ -249,7 +250,7 @@ Signal Signal_receiver::pending_signal()
 		context._curr_signal = Signal::Data(0, 0);
 
 		Trace::Signal_received trace_event(context, result.num);
-		throw Context_ring::Break_for_each();
+		return true;
 	});
 	if (result.context) {
 		Mutex::Guard context_guard(result.context->_mutex);
@@ -268,10 +269,9 @@ Signal Signal_receiver::pending_signal()
 	 * signal, we may have increased the semaphore already. In this case
 	 * the signal-causing context is absent from the list.
 	 */
-	throw Signal_not_pending();
+	return Signal();
 }
 
-
 void Signal_receiver::unblock_signal_waiter(Rpc_entrypoint &)
 {
 	_signal_available.up();

repos/base/src/lib/base/signal_common.cc

@@ -149,9 +149,10 @@ Signal Signal_receiver::wait_for_signal()
 {
 	for (;;) {
 
-		try {
-			return pending_signal();
-		} catch (Signal_not_pending) { }
+		Signal sig = pending_signal();
+
+		if (sig.valid())
+			return sig;
 
 		/* block until the receiver has received a signal */
 		block_for_signal();

repos/ports/src/virtualbox5/thread.cc

@@ -160,8 +160,6 @@ extern "C" int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
 			log("Upgrading memory for creation of "
 			    "thread '", Cstring(rtthread->szName), "'");
 			cpu_connection(rtthread->enmType)->upgrade_ram(4096);
-		} catch (Genode::Signal_receiver::Signal_not_pending) {
-			error("signal not pending ?");
 		} catch (Out_of_caps) {
 			error("out of caps ...");
 		}