From 4f6b3f30f048632a763bbd552b3c0c4dbc7af7e0 Mon Sep 17 00:00:00 2001
From: Zoltan Varga <vargaz@gmail.com>
Date: Mon, 30 Mar 2020 08:36:22 -0400
Subject: [PATCH] [wasm] Throw an exception in some blocking operations in
 non-threaded mode. (#19363)

* [wasm] Throw an exception from Monitor.Wait () in non-threaded mode.

* [wasm] Throw an exception when waiting for unsignalled events in non-threaded mode.
---
 mono/metadata/monitor.c   |  7 +++++++
 mono/metadata/threads.c   | 16 ++++++++++++++++
 mono/metadata/w32handle.c | 28 ++++++++++++++++++++++++++++
 mono/metadata/w32handle.h |  6 ++++++
 4 files changed, 57 insertions(+)

diff --git a/mono/metadata/monitor.c b/mono/metadata/monitor.c
index 643af9ba177..72e51bd56c5 100644
--- a/mono/metadata/monitor.c
+++ b/mono/metadata/monitor.c
@@ -1409,6 +1409,13 @@ mono_monitor_wait (MonoObjectHandle obj_handle, guint32 ms, MonoBoolean allow_in
 		mono_error_set_pending_exception (error);
 		return FALSE;
 	}
+
+#ifdef DISABLE_THREADS
+	if (ms == MONO_INFINITE_WAIT) {
+		mono_error_set_synchronization_lock (error, "Cannot wait on monitors on this runtime.");
+		return FALSE;
+	}
+#endif
 	
 	LOCK_DEBUG (g_message ("%s: (%d) queuing handle %p", __func__, id, event));
 
diff --git a/mono/metadata/threads.c b/mono/metadata/threads.c
index f28e0bdc8e9..684aa2e7919 100644
--- a/mono/metadata/threads.c
+++ b/mono/metadata/threads.c
@@ -2314,6 +2314,22 @@ ves_icall_System_Threading_WaitHandle_Wait_internal (gpointer *handles, gint32 n
 
 	MonoW32HandleWaitRet ret;
 
+#ifdef DISABLE_THREADS
+	if (numhandles == 1 && timeout == MONO_INFINITE_WAIT) {
+		gboolean signalled = FALSE;
+		for (int i = 0; i < numhandles; ++i) {
+			if (mono_w32handle_handle_is_owned (handles [i]) || mono_w32handle_handle_is_signalled (handles [i])) {
+				signalled = TRUE;
+				break;
+			}
+		}
+		if (!signalled) {
+			mono_error_set_synchronization_lock (error, "Cannot wait on events on this runtime.");
+			return 0;
+		}
+	}
+#endif
+
 	HANDLE_LOOP_PREPARE;
 
 	for (;;) {
diff --git a/mono/metadata/w32handle.c b/mono/metadata/w32handle.c
index 5f064b5aa52..17a4b9d68dd 100644
--- a/mono/metadata/w32handle.c
+++ b/mono/metadata/w32handle.c
@@ -815,6 +815,34 @@ own_if_owned (MonoW32Handle *handle_data, gboolean *abandoned)
 	return TRUE;
 }
 
+gboolean
+mono_w32handle_handle_is_signalled (gpointer handle)
+{
+	MonoW32Handle *handle_data;
+	gboolean res;
+
+	if (!mono_w32handle_lookup_and_ref (handle, &handle_data))
+		return FALSE;
+
+	res = mono_w32handle_issignalled (handle_data);
+	mono_w32handle_unref (handle_data);
+	return res;
+}
+
+gboolean
+mono_w32handle_handle_is_owned (gpointer handle)
+{
+	MonoW32Handle *handle_data;
+	gboolean res;
+
+	if (!mono_w32handle_lookup_and_ref (handle, &handle_data))
+		return FALSE;
+
+	res = mono_w32handle_ops_isowned (handle_data);
+	mono_w32handle_unref (handle_data);
+	return res;
+}
+
 #ifdef HOST_WIN32
 MonoW32HandleWaitRet
 mono_w32handle_wait_one (gpointer handle, guint32 timeout, gboolean alertable)
diff --git a/mono/metadata/w32handle.h b/mono/metadata/w32handle.h
index 215606314f3..d0c50a9357b 100644
--- a/mono/metadata/w32handle.h
+++ b/mono/metadata/w32handle.h
@@ -154,6 +154,12 @@ mono_w32handle_trylock (MonoW32Handle *handle_data);
 void
 mono_w32handle_unlock (MonoW32Handle *handle_data);
 
+gboolean
+mono_w32handle_handle_is_signalled (gpointer handle);
+
+gboolean
+mono_w32handle_handle_is_owned (gpointer handle);
+
 MonoW32HandleWaitRet
 mono_w32handle_wait_one (gpointer handle, guint32 timeout, gboolean alertable);
 
-- 
2.11.4.GIT