Use pthread_join from musl (#15604)

Author: kleisauke

system/lib/libc/musl/src/thread/pthread_join.c

@@ -7,34 +7,75 @@ static void dummy1(pthread_t t)
 }
 weak_alias(dummy1, __tl_sync);
 
+#ifdef __EMSCRIPTEN__ // XXX Emscripten add extern for __emscripten_thread_cleanup
+extern void __emscripten_thread_cleanup(pthread_t thread);
+#endif
+
 static int __pthread_timedjoin_np(pthread_t t, void **res, const struct timespec *at)
 {
+#ifdef __EMSCRIPTEN__
+	// Attempt to join a thread which does not point to a valid thread, or
+	// does not exist anymore.
+	if (t->self != t) return ESRCH;
+	// Thread is attempting to join to itself.  Already detached threads are
+	// handled below by returning EINVAL instead.
+	// TODO: The detached check here is just to satisfy the `other.test_{proxy,main}_pthread_join_detach` tests.
+	if (t->detach_state != DT_DETACHED && __pthread_self() == t) return EDEADLK;
+#endif
 	int state, cs, r = 0;
 	__pthread_testcancel();
 	__pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
 	if (cs == PTHREAD_CANCEL_ENABLE) __pthread_setcancelstate(cs, 0);
 	while ((state = t->detach_state) && r != ETIMEDOUT && r != EINVAL) {
+#ifdef __EMSCRIPTEN__
+		// The thread is (already) detached and therefore not joinable.
+		// This also handle cases where the thread becomes detached
+		// *during* the join.
+		if (state >= DT_DETACHED) {
+			// Even though the man page says this is undefined
+			// behaviour we ave several tests in the posixtest suite
+			// that depend on this.
+			r = EINVAL;
+			break;
+		}
+#else
 		if (state >= DT_DETACHED) a_crash();
+#endif
 		r = __timedwait_cp(&t->detach_state, state, CLOCK_REALTIME, at, 1);
 	}
 	__pthread_setcancelstate(cs, 0);
 	if (r == ETIMEDOUT || r == EINVAL) return r;
 	__tl_sync(t);
 	if (res) *res = t->result;
+#ifdef __EMSCRIPTEN__
+	// Thread was exited during this call, be sure to clean it up.
+	if (state == DT_EXITED) __emscripten_thread_cleanup(t);
+#else // XXX Emscripten map_base unused
 	if (t->map_base) __munmap(t->map_base, t->map_size);
+#endif
 	return 0;
 }
 
 int __pthread_join(pthread_t t, void **res)
 {
+#ifdef __EMSCRIPTEN__ // XXX Emscripten check whether blocking is allowed.
+	emscripten_check_blocking_allowed();
+#endif
 	return __pthread_timedjoin_np(t, res, 0);
 }
 
 static int __pthread_tryjoin_np(pthread_t t, void **res)
 {
+#ifdef __EMSCRIPTEN__ // XXX Emscripten call __pthread_timedjoin_np directly to avoid additional check
+	return t->detach_state==DT_JOINABLE ? EBUSY : __pthread_timedjoin_np(t, res, 0);
+#else
 	return t->detach_state==DT_JOINABLE ? EBUSY : __pthread_join(t, res);
+#endif
 }
 
 weak_alias(__pthread_tryjoin_np, pthread_tryjoin_np);
 weak_alias(__pthread_timedjoin_np, pthread_timedjoin_np);
 weak_alias(__pthread_join, pthread_join);
+#ifdef __EMSCRIPTEN__ // XXX Emscripten add an extra alias for LSan
+weak_alias(__pthread_join, emscripten_builtin_pthread_join);
+#endif

system/lib/pthread/pthread_create.c

@@ -247,16 +247,14 @@ void _emscripten_thread_exit(void* result) {
    * call; the loser is responsible for freeing thread resources. */
   int state = a_cas(&self->detach_state, DT_JOINABLE, DT_EXITING);
 
-  // Mark the thread as no longer running.
-  // When we publish this, the main thread is free to deallocate the thread
-  // object and we are done.
   if (state == DT_DETACHED) {
-    self->detach_state = DT_EXITED;
     __emscripten_thread_cleanup(self);
   } else {
-    self->detach_state = DT_EXITING;
-    // wake any threads that might be waiting for us to exit
-    emscripten_futex_wake(&self->detach_state, INT_MAX);
+    // Mark the thread as no longer running, so it can be joined.
+    // Once we publish this, any threads that are waiting to join with us can
+    // proceed and this worker can be recycled and used on another thread.
+    a_store(&self->detach_state, DT_EXITED);
+    __wake(&self->detach_state, 1, 1); // Wake any joiner.
   }
 }
 

system/lib/pthread/pthread_join.c

@@ -827,15 +827,14 @@ def get_files(self):
         'syscall_cp.c', 'tls.c',
         # TODO: Support this. See #12216.
         'pthread_setname_np.c',
-        # TODO: These could be moved away from JS in the upcoming musl upgrade.
-        'pthread_join.c', 'pthread_testcancel.c',
+        # TODO: Prefer to use the musl implementation.
+        'pthread_testcancel.c',
       ]
       libc_files += files_in_path(
         path='system/lib/pthread',
         filenames=[
           'library_pthread.c',
           'pthread_create.c',
-          'pthread_join.c',
           'pthread_testcancel.c',
           'emscripten_proxy_main.c',
           'emscripten_thread_init.c',