base-hw: Ada/SPARK-friendly Ipc_node interface

This prevents the use of C++ features in the public method interface of the
synchronous-IPC module that would be impractical for the in-place
translation of the module into Ada in the context of the Spunky project.

* Get rid of thread accessor.
* Get rid of non-const functions with return values.
* Get rid of pointer return-values.

Ref #3308

repos/base-hw/src/core/kernel/ipc_node.cc

@@ -122,8 +122,8 @@ void Ipc_node::send_request(Ipc_node &callee, bool help)
 }
 
 
-Ipc_node * Ipc_node::helping_sink() {
+Thread &Ipc_node::helping_sink() {
-	return _helps_outbuf_dst() ? _callee->helping_sink() : this; }
+	return _helps_outbuf_dst() ? _callee->helping_sink() : _thread; }
 
 
 bool Ipc_node::can_await_request()
@@ -132,18 +132,12 @@ bool Ipc_node::can_await_request()
 }
 
 
-bool Ipc_node::await_request()
+void Ipc_node::await_request()
 {
-	/* if no request announced then wait */
-	bool announced = false;
 	_state = AWAIT_REQUEST;
-
-	/* if anybody already announced a request receive it */
 	_request_queue.dequeue([&] (Queue_item &item) {
 		_receive_request(item.object());
-		announced = true;
 	});
-	return announced;
 }
 
 

repos/base-hw/src/core/kernel/ipc_node.h

@@ -124,12 +124,13 @@ class Kernel::Ipc_node
 		 * \param help      wether the request implies a helping relationship
 		 */
 		bool can_send_request();
-		void send_request(Ipc_node &callee, bool help);
+		void send_request(Ipc_node &callee,
+		                  bool      help);
 
 		/**
 		 * Return root destination of the helping-relation tree we are in
 		 */
-		Ipc_node * helping_sink();
+		Thread &helping_sink();
 
 		/**
 		 * Call function 'f' of type 'void (Ipc_node *)' for each helper
@@ -137,12 +138,12 @@ class Kernel::Ipc_node
 		template <typename F> void for_each_helper(F f)
 		{
 			/* if we have a helper in the receive buffer, call 'f' for it */
-			if (_caller && _caller->_help) f(*_caller);
+			if (_caller && _caller->_help) f(_caller->_thread);
 
 			/* call 'f' for each helper in our request queue */
 			_request_queue.for_each([f] (Queue_item &item) {
 				Ipc_node &node { item.object() };
-				if (node._help) f(node);
+				if (node._help) f(node._thread);
 			});
 		}
 
@@ -152,7 +153,7 @@ class Kernel::Ipc_node
 		 * \return  wether a request could be received already
 		 */
 		bool can_await_request();
-		bool await_request();
+		void await_request();
 
 		/**
 		 * Reply to last request if there's any
@@ -164,12 +165,7 @@ class Kernel::Ipc_node
 		 */
 		void cancel_waiting();
 
-
+		bool awaits_request() const { return _state == AWAIT_REQUEST; }
-		/***************
-		 ** Accessors **
-		 ***************/
-
-		Thread &thread() { return _thread; }
 };
 
 #endif /* _CORE__KERNEL__IPC_NODE_H_ */

repos/base-hw/src/core/kernel/thread.cc

@@ -217,15 +217,15 @@ void Thread::ipc_await_request_failed()
 void Thread::_deactivate_used_shares()
 {
 	Cpu_job::_deactivate_own_share();
-	_ipc_node.for_each_helper([&] (Ipc_node &ipc_node) {
+	_ipc_node.for_each_helper([&] (Thread &thread) {
-		ipc_node.thread()._deactivate_used_shares(); });
+		thread._deactivate_used_shares(); });
 }
 
 void Thread::_activate_used_shares()
 {
 	Cpu_job::_activate_own_share();
-	_ipc_node.for_each_helper([&] (Ipc_node &ipc_node) {
+	_ipc_node.for_each_helper([&] (Thread &thread) {
-		ipc_node.thread()._activate_used_shares(); });
+		thread._activate_used_shares(); });
 }
 
 void Thread::_become_active()
@@ -246,7 +246,7 @@ void Thread::_die() { _become_inactive(DEAD); }
 
 
 Cpu_job * Thread::helping_sink() {
-	return &_ipc_node.helping_sink()->thread(); }
+	return &_ipc_node.helping_sink(); }
 
 
 size_t Thread::_core_to_kernel_quota(size_t const quota) const
@@ -405,22 +405,23 @@ void Thread::_call_delete_thread()
 
 void Thread::_call_await_request_msg()
 {
-	if (!_ipc_node.can_await_request()) {
+	if (_ipc_node.can_await_request()) {
-		Genode::raw("IPC await request: bad state");
-		user_arg_0(0);
-		return;
-	}
 		unsigned const rcv_caps = user_arg_1();
 		Genode::Allocator &slab = pd().platform_pd().capability_slab();
 		for (unsigned i = 0; i < rcv_caps; i++)
 			_obj_id_ref_ptr[i] = slab.alloc(sizeof(Object_identity_reference));
 
 		_ipc_rcv_caps = rcv_caps;
-	if (_ipc_node.await_request()) {
+		_ipc_node.await_request();
-		user_arg_0(0);
+		if (_ipc_node.awaits_request()) {
-		return;
-	}
 			_become_inactive(AWAITS_IPC);
+		} else {
+			user_arg_0(0);
+		}
+	} else {
+		Genode::raw("IPC await request: bad state");
+		user_arg_0(0);
+	}
 }