libc: support detached pthreads

Fixes #3880

repos/libports/lib/symbols/libc

@@ -976,6 +976,7 @@ _ZN4Libc7suspendERNS_15Suspend_functorEm T
 _Z16pthread_registryv T
 _ZN4Libc16Pthread_registry6insertERNS_7PthreadE T
 _ZN4Libc16Pthread_registry6removeERNS_7PthreadE T
+_ZN4Libc16Pthread_registry7cleanupEPNS_7PthreadE T
 _ZN4Libc16Pthread_registry8containsERNS_7PthreadE T
 _ZN4Libc14pthread_createEPP7pthreadPFPvS3_ES3_mPKcPN6Genode11Cpu_sessionENS8_8Affinity8LocationE T
 _ZN4Libc14pthread_createEPP7pthreadRN6Genode6ThreadE T

repos/libports/src/lib/libc/internal/pthread.h

@@ -18,6 +18,7 @@
 
 /* Genode includes */
 #include <base/blockade.h>
+#include <base/sleep.h>
 #include <libc/allocator.h>
 #include <libc/component.h>
 #include <util/reconstructible.h>
@@ -51,6 +52,9 @@ class Libc::Pthread_registry
 
 		Pthread *_array[MAX_NUM_PTHREADS] = { 0 };
 
+		/* thread to be destroyed on next 'cleanup()' call */
+		Pthread *_cleanup_thread { nullptr };
+
 	public:
 
 		void insert(Pthread &thread);
@@ -58,6 +62,9 @@ class Libc::Pthread_registry
 		void remove(Pthread &thread);
 
 		bool contains(Pthread &thread);
+
+		/* destroy '_cleanup_thread' and register another one if given */
+		void cleanup(Pthread *new_cleanup_thread = nullptr);
 };
 
 
@@ -68,8 +75,9 @@ extern "C" {
 
 	struct pthread_attr
 	{
-		void   *stack_addr { nullptr };
-		size_t  stack_size { Libc::Component::stack_size() };
+		void   *stack_addr   { nullptr };
+		size_t  stack_size   { Libc::Component::stack_size() };
+		int     detach_state { PTHREAD_CREATE_JOINABLE };
 	};
 
 	/*
@@ -160,6 +168,7 @@ struct Libc::Pthread : Noncopyable, Thread::Tls::Base
 		void _associate_thread_with_pthread()
 		{
 			Thread::Tls::Base::tls(_thread, *this);
+			pthread_registry().cleanup();
 			pthread_registry().insert(*this);
 		}
 
@@ -174,6 +183,8 @@ struct Libc::Pthread : Noncopyable, Thread::Tls::Base
 		 */
 		Genode::Mutex _mutex { };
 
+		Genode::Blockade _detach_blockade;
+
 		/* return value for 'pthread_join()' */
 		void *_retval = PTHREAD_CANCELED;
 
@@ -243,17 +254,29 @@ struct Libc::Pthread : Noncopyable, Thread::Tls::Base
 
 		void join(void **retval);
 
+		int detach();
+
 		/*
 		 * Inform the thread calling 'pthread_join()' that this thread can be
 		 * destroyed.
 		 */
 		void cancel();
 
-		void exit(void *retval)
+		void exit(void *retval) __attribute__((noreturn))
 		{
 			while (cleanup_pop(1)) { }
 			_retval = retval;
 			cancel();
+
+			/*
+			 * Block until the thread is destroyed by 'pthread_join()' or
+			 * register the thread for destruction if it is in detached state.
+			 */
+
+			_detach_blockade.block();
+
+			pthread_registry().cleanup(this);
+			sleep_forever();
 		}
 
 		void   *stack_addr() const { return _stack_addr; }

repos/libports/src/lib/libc/pthread.cc

@@ -14,7 +14,6 @@
 
 /* Genode includes */
 #include <base/log.h>
-#include <base/sleep.h>
 #include <base/thread.h>
 #include <util/list.h>
 #include <libc/allocator.h>
@@ -93,6 +92,13 @@ void Libc::Pthread::join(void **retval)
 }
 
 
+int Libc::Pthread::detach()
+{
+	_detach_blockade.wakeup();
+	return 0;
+}
+
+
 void Libc::Pthread::cancel()
 {
 	Genode::Mutex::Guard guard(_mutex);
@@ -147,6 +153,20 @@ bool Libc::Pthread_registry::contains(Pthread &thread)
 }
 
 
+void Libc::Pthread_registry::cleanup(Pthread *new_cleanup_thread)
+{
+	static Mutex cleanup_mutex;
+	Mutex::Guard guard(cleanup_mutex);
+
+	if (_cleanup_thread) {
+		Libc::Allocator alloc { };
+		destroy(alloc, _cleanup_thread);
+	}
+
+	_cleanup_thread = new_cleanup_thread;
+}
+
+
 Libc::Pthread_registry &pthread_registry()
 {
 	static Libc::Pthread_registry instance;
@@ -558,7 +578,6 @@ extern "C" {
 	void pthread_exit(void *value_ptr)
 	{
 		pthread_self()->exit(value_ptr);
-		sleep_forever();
 	}
 
 	typeof(pthread_exit) _pthread_exit
@@ -614,6 +633,34 @@ extern "C" {
 	pthread_t __sys_thr_self(void);
 
 
+	int pthread_attr_getdetachstate(const pthread_attr_t *attr, int *detachstate)
+	{
+		if (!attr || !*attr || !detachstate)
+			return EINVAL;
+
+		*detachstate = (*attr)->detach_state;
+
+		return 0;
+	}
+
+	typeof(pthread_attr_getdetachstate) _pthread_attr_getdetachstate
+		__attribute__((alias("pthread_attr_getdetachstate")));
+
+
+	int pthread_attr_setdetachstate(pthread_attr_t *attr, int detachstate)
+	{
+		if (!attr || !*attr)
+			return EINVAL;
+
+		(*attr)->detach_state = detachstate;
+
+		return 0;
+	}
+
+	typeof(pthread_attr_setdetachstate) _pthread_attr_setdetachstate
+		__attribute__((alias("pthread_attr_setdetachstate")));
+
+
 	int pthread_attr_setstacksize(pthread_attr_t *attr, size_t stacksize)
 	{
 		if (!attr || !*attr)
@@ -692,6 +739,15 @@ extern "C" {
 		__attribute__((alias("pthread_equal")));
 
 
+	int pthread_detach(pthread_t thread)
+	{
+		return thread->detach();
+	}
+
+	typeof(pthread_detach) _pthread_detach
+		__attribute__((alias("pthread_detach")));
+
+
 	void __pthread_cleanup_push_imp(void (*routine)(void*), void *arg,
 	                                struct _pthread_cleanup_info *)
 	{

repos/libports/src/lib/libc/pthread_create.cc

@@ -141,9 +141,15 @@ extern "C"
 		if (_verbose)
 			Genode::log("create ", pthread_name, " -> cpu ", cpu);
 
-		return Libc::pthread_create(thread, start_routine, arg, stack_size,
-		                            pthread_name.string(), _cpu_session,
-		                            location);
+		int result = Libc::pthread_create(thread, start_routine, arg, stack_size,
+		                                  pthread_name.string(), _cpu_session,
+		                                  location);
+
+		if ((result == 0) && attr && *attr &&
+		    ((*attr)->detach_state == PTHREAD_CREATE_DETACHED))
+			pthread_detach(*thread);
+
+		return result;
 	}
 
 	typeof(pthread_create) _pthread_create