Remove exceptions from Cpu_session interface

The 'Thread_creation_failed' error is now reflected as
'Thread::Start_result' return value. This change also removes the
use of 'Invalid_thread' within core as this exception is an alias
of Cpu_session::Thread_creation_failed.

Issue #5245

repos/base-linux/src/core/include/irq_object.h

@@ -43,7 +43,7 @@ class Core::Irq_object : public Thread
 		void sigh(Signal_context_capability cap);
 		void ack_irq();
 
-		void start() override;
+		Start_result start() override;
 
 };
 

repos/base-linux/src/core/spec/linux/irq_session_component.cc

@@ -75,9 +75,10 @@ void Irq_object::ack_irq()
 }
 
 
-void Irq_object::start()
+Thread::Start_result Irq_object::start()
 {
 	warning(__func__, " not implemented");
+	return Start_result::DENIED;
 }
 
 

repos/base-linux/src/core/spec/pc/irq_session_component.cc

@@ -110,10 +110,11 @@ void Irq_object::ack_irq()
 }
 
 
-void Irq_object::start()
+Thread::Start_result Irq_object::start()
 {
-	Thread::start();
+	Start_result const result = Thread::start();
 	_sync_bootup.block();
+	return result;
 }
 
 

repos/base-linux/src/core/thread_linux.cc

@@ -64,8 +64,9 @@ void Thread::_init_platform_thread(size_t, Type) { }
 void Thread::_deinit_platform_thread() { }
 
 
-void Thread::start()
+Thread::Start_result Thread::start()
 {
 	native_thread().tid = lx_create_thread(Thread::_thread_start, stack_top());
 	native_thread().pid = lx_getpid();
+	return Start_result::OK;
 }

repos/base-linux/src/lib/base/child_process.cc

@@ -24,6 +24,16 @@
 using namespace Genode;
 
 
+static Thread_capability create_thread(auto &pd, auto &cpu, auto const &name)
+{
+	return cpu.create_thread(pd, name, { }, { }).template convert<Thread_capability>(
+		[&] (Thread_capability cap) { return cap; },
+		[&] (Cpu_session::Create_thread_error) {
+			error("failed to create thread via CPU session");
+			return Thread_capability(); });
+}
+
+
 /*
  * Register main thread at core
  *
@@ -35,8 +45,7 @@ Child::Initial_thread::Initial_thread(Cpu_session          &cpu,
                                       Pd_session_capability pd,
                                       Name           const &name)
 :
-	_cpu(cpu),
-	_cap(cpu.create_thread(pd, name, Affinity::Location(), Cpu_session::Weight()))
+	_cpu(cpu), _cap(create_thread(pd, cpu, name))
 { }
 
 

repos/base-linux/src/lib/base/thread_linux.cc

@@ -110,10 +110,12 @@ void Thread::_init_platform_thread(size_t /* weight */, Type type)
 
 	/* for normal threads create an object at the CPU session */
 	if (type == NORMAL) {
-		_thread_cap = _cpu_session->create_thread(pd_session_cap(),
-		                                          _stack->name().string(),
-		                                          Affinity::Location(),
-		                                          Weight());
+		_cpu_session->create_thread(pd_session_cap(), _stack->name().string(),
+		                            Affinity::Location(), Weight()).with_result(
+			[&] (Thread_capability cap) { _thread_cap = cap; },
+			[&] (Cpu_session::Create_thread_error) {
+				error("Thread::_init_platform_thread: create_thread failed");
+			});
 		return;
 	}
 	/* adjust initial object state for main threads */
@@ -152,11 +154,13 @@ void Thread::_deinit_platform_thread()
 	}
 
 	/* inform core about the killed thread */
-	_cpu_session->kill_thread(_thread_cap);
+	_thread_cap.with_result(
+		[&] (Thread_capability cap) { _cpu_session->kill_thread(cap); },
+		[&] (Cpu_session::Create_thread_error) { });
 }
 
 
-void Thread::start()
+Thread::Start_result Thread::start()
 {
 	/* synchronize calls of the 'start' function */
 	static Mutex mutex;
@@ -181,6 +185,8 @@ void Thread::start()
 
 	/* wait until the 'thread_start' function got entered */
 	startup_lock().block();
+
+	return Start_result::OK;
 }
 
 

repos/base-linux/src/lib/lx_hybrid/lx_hybrid.cc

@@ -493,12 +493,13 @@ Thread *Thread::myself()
 }
 
 
-void Thread::start()
+Thread::Start_result Thread::start()
 {
 	/*
 	 * Unblock thread that is supposed to slumber in 'thread_start'.
 	 */
 	native_thread().meta_data->started();
+	return Start_result::OK;
 }
 
 
@@ -531,9 +532,14 @@ Thread::Thread(size_t weight, const char *name, size_t /* stack size */,
 
 	_thread_cap = _cpu_session->create_thread(_env_ptr->pd_session_cap(), name,
 	                                          Location(), Weight(weight));
-
-	Linux_native_cpu_client native_cpu(_cpu_session->native_cpu());
-	native_cpu.thread_id(_thread_cap, native_thread().pid, native_thread().tid);
+	_thread_cap.with_result(
+		[&] (Thread_capability cap) {
+			Linux_native_cpu_client native_cpu(_cpu_session->native_cpu());
+			native_cpu.thread_id(cap, native_thread().pid, native_thread().tid);
+		},
+		[&] (Cpu_session::Create_thread_error) {
+			error("failed to create hybrid thread"); }
+	);
 }
 
 
@@ -573,7 +579,9 @@ Thread::~Thread()
 	_native_thread = nullptr;
 
 	/* inform core about the killed thread */
-	_cpu_session->kill_thread(_thread_cap);
+	_thread_cap.with_result(
+		[&] (Thread_capability cap) { _cpu_session->kill_thread(cap); },
+		[&] (Cpu_session::Create_thread_error) { });
 }