[browser][MT] assert no managed transition on UI thread after start

src/mono/browser/runtime/exports-internal.ts

@@ -127,6 +127,9 @@ export function cwraps_internal (internal: any): void {
 
 /* @deprecated not GC safe, legacy support for Blazor */
 export function monoObjectAsBoolOrNullUnsafe (obj: MonoObject): boolean | null {
+    // TODO https://github.com/dotnet/runtime/issues/100411
+    // after Blazor stops using monoObjectAsBoolOrNullUnsafe
+
     if (obj === MonoObjectNull) {
         return null;
     }

src/mono/browser/runtime/gc-lock.ts

@@ -7,6 +7,9 @@ import cwraps from "./cwraps";
 
 export let gc_locked = false;
 
+// TODO https://github.com/dotnet/runtime/issues/100411
+// after Blazor stops using mono_wasm_gc_lock, mono_wasm_gc_unlock
+
 export function mono_wasm_gc_lock (): void {
     if (gc_locked) {
         throw new Error("GC is already locked");

src/mono/browser/runtime/marshal-to-cs.ts

@@ -22,7 +22,6 @@ import { _zero_region, localHeapViewF64, localHeapViewI32, localHeapViewU8 } fro
 import { stringToMonoStringRoot, stringToUTF16 } from "./strings";
 import { JSMarshalerArgument, JSMarshalerArguments, JSMarshalerType, MarshalerToCs, MarshalerToJs, BoundMarshalerToCs, MarshalerType } from "./types/internal";
 import { TypedArray } from "./types/emscripten";
-import { gc_locked } from "./gc-lock";
 
 export const jsinteropDoc = "For more information see https://aka.ms/dotnet-wasm-jsinterop";
 
@@ -224,6 +223,7 @@ function _marshal_string_to_cs_impl (arg: JSMarshalerArgument, value: string) {
         set_arg_intptr(arg, buffer);
         set_arg_length(arg, value.length);
     } else {
+        mono_assert(!WasmEnableThreads, "Marshaling strings by reference is not supported in multithreaded mode");
         const root = get_string_root(arg);
         try {
             stringToMonoStringRoot(value, root);
@@ -463,7 +463,7 @@ export function marshal_array_to_cs_impl (arg: JSMarshalerArgument, value: Array
             mono_check(Array.isArray(value), "Value is not an Array");
             _zero_region(buffer_ptr, buffer_length);
             if (!WasmEnableJsInteropByValue) {
-                mono_assert(!WasmEnableThreads || !gc_locked, "GC must not be locked when creating a GC root");
+                mono_assert(!WasmEnableThreads, "Marshaling strings by reference is not supported in multithreaded mode");
                 cwraps.mono_wasm_register_root(buffer_ptr, buffer_length, "marshal_array_to_cs");
             }
             for (let index = 0; index < length; index++) {
@@ -474,7 +474,7 @@ export function marshal_array_to_cs_impl (arg: JSMarshalerArgument, value: Array
             mono_check(Array.isArray(value), "Value is not an Array");
             _zero_region(buffer_ptr, buffer_length);
             if (!WasmEnableJsInteropByValue) {
-                mono_assert(!WasmEnableThreads || !gc_locked, "GC must not be locked when creating a GC root");
+                mono_assert(!WasmEnableThreads, "Marshaling objects by reference is not supported in multithreaded mode");
                 cwraps.mono_wasm_register_root(buffer_ptr, buffer_length, "marshal_array_to_cs");
             }
             for (let index = 0; index < length; index++) {

src/mono/browser/runtime/marshal-to-js.ts

@@ -22,7 +22,6 @@ import { TypedArray } from "./types/emscripten";
 import { get_marshaler_to_cs_by_type, jsinteropDoc, marshal_exception_to_cs } from "./marshal-to-cs";
 import { localHeapViewF64, localHeapViewI32, localHeapViewU8 } from "./memory";
 import { call_delegate } from "./managed-exports";
-import { gc_locked } from "./gc-lock";
 import { mono_log_debug } from "./logging";
 import { invoke_later_when_on_ui_thread_async } from "./invoke-js";
 
@@ -390,6 +389,7 @@ export function marshal_string_to_js (arg: JSMarshalerArgument): string | null {
         Module._free(buffer as any);
         return value;
     } else {
+        mono_assert(!WasmEnableThreads, "Marshaling strings by reference is not supported in multithreaded mode");
         const root = get_string_root(arg);
         try {
             const value = monoStringToString(root);
@@ -504,7 +504,7 @@ function _marshal_array_to_js_impl (arg: JSMarshalerArgument, element_type: Mars
             result[index] = marshal_string_to_js(element_arg);
         }
         if (!WasmEnableJsInteropByValue) {
-            mono_assert(!WasmEnableThreads || !gc_locked, "GC must not be locked when disposing a GC root");
+            mono_assert(!WasmEnableThreads, "Marshaling string by reference is not supported in multithreaded mode");
             cwraps.mono_wasm_deregister_root(<any>buffer_ptr);
         }
     } else if (element_type == MarshalerType.Object) {
@@ -514,7 +514,7 @@ function _marshal_array_to_js_impl (arg: JSMarshalerArgument, element_type: Mars
             result[index] = _marshal_cs_object_to_js(element_arg);
         }
         if (!WasmEnableJsInteropByValue) {
-            mono_assert(!WasmEnableThreads || !gc_locked, "GC must not be locked when disposing a GC root");
+            mono_assert(!WasmEnableThreads, "Marshaling objects by reference is not supported in multithreaded mode");
             cwraps.mono_wasm_deregister_root(<any>buffer_ptr);
         }
     } else if (element_type == MarshalerType.JSObject) {

src/mono/browser/runtime/roots.ts

@@ -4,7 +4,7 @@
 import WasmEnableThreads from "consts:wasmEnableThreads";
 
 import cwraps from "./cwraps";
-import { Module, mono_assert } from "./globals";
+import { Module, mono_assert, runtimeHelpers } from "./globals";
 import { VoidPtr, ManagedPointer, NativePointer } from "./types/emscripten";
 import { MonoObjectRef, MonoObjectRefNull, MonoObject, is_nullish, WasmRoot, WasmRootBuffer } from "./types/internal";
 import { _zero_region, localHeapViewU32 } from "./memory";
@@ -24,6 +24,7 @@ const _external_root_free_instances: WasmExternalRoot<any>[] = [];
  * For small numbers of roots, it is preferable to use the mono_wasm_new_root and mono_wasm_new_roots APIs instead.
  */
 export function mono_wasm_new_root_buffer (capacity: number, name?: string): WasmRootBuffer {
+    if (WasmEnableThreads && runtimeHelpers.disableManagedTransition) throw new Error("External roots are not supported when threads are enabled");
     if (capacity <= 0)
         throw new Error("capacity >= 1");
 
@@ -44,6 +45,7 @@ export function mono_wasm_new_root_buffer (capacity: number, name?: string): Was
  * Releasing this root will not de-allocate the root space. You still need to call .release().
  */
 export function mono_wasm_new_external_root<T extends MonoObject> (address: VoidPtr | MonoObjectRef): WasmRoot<T> {
+    if (WasmEnableThreads && runtimeHelpers.disableManagedTransition) throw new Error("External roots are not supported in multithreaded mode");
     let result: WasmExternalRoot<T>;
 
     if (!address)
@@ -67,6 +69,7 @@ export function mono_wasm_new_external_root<T extends MonoObject> (address: Void
  * When you are done using the root you must call its .release() method.
  */
 export function mono_wasm_new_root<T extends MonoObject> (value: T | undefined = undefined): WasmRoot<T> {
+    if (WasmEnableThreads && runtimeHelpers.disableManagedTransition) throw new Error("External roots are not supported in multithreaded mode");
     let result: WasmRoot<T>;
 
     if (_scratch_root_free_instances.length > 0) {

src/mono/browser/runtime/startup.ts

@@ -288,14 +288,16 @@ async function onRuntimeInitializedAsync (userOnRuntimeInitialized: () => void)
                 runtimeHelpers.ioThreadTID = tcwraps.mono_wasm_create_io_thread();
             }
 
-            // TODO make UI thread not managed
+            // TODO make UI thread not managed/attached https://github.com/dotnet/runtime/issues/100411
             tcwraps.mono_wasm_register_ui_thread();
             monoThreadInfo.isAttached = true;
             monoThreadInfo.isRegistered = true;
 
             runtimeHelpers.runtimeReady = true;
             update_thread_info();
             bindings_init();
+
+            runtimeHelpers.disableManagedTransition = true;
         } else {
             // load mono runtime and apply environment settings (if necessary)
             await start_runtime();

src/mono/browser/runtime/strings.ts

@@ -1,6 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+import WasmEnableThreads from "consts:wasmEnableThreads";
+
 import { mono_wasm_new_root, mono_wasm_new_root_buffer } from "./roots";
 import { MonoString, MonoStringNull, WasmRoot, WasmRootBuffer } from "./types/internal";
 import { Module } from "./globals";
@@ -118,6 +120,10 @@ export function stringToUTF16Ptr (str: string): VoidPtr {
 }
 
 export function monoStringToString (root: WasmRoot<MonoString>): string | null {
+    // TODO https://github.com/dotnet/runtime/issues/100411
+    // after Blazor stops using monoStringToStringUnsafe
+    // mono_assert(!WasmEnableThreads, "Marshaling strings by reference is not supported in multithreaded mode");
+
     if (root.value === MonoStringNull)
         return null;
 
@@ -152,6 +158,7 @@ export function monoStringToString (root: WasmRoot<MonoString>): string | null {
 }
 
 export function stringToMonoStringRoot (string: string, result: WasmRoot<MonoString>): void {
+    if (WasmEnableThreads) return;
     result.clear();
 
     if (string === null)

src/mono/browser/runtime/types/internal.ts

@@ -206,6 +206,7 @@ export type RuntimeHelpers = {
     getMemory(): WebAssembly.Memory,
     getWasmIndirectFunctionTable(): WebAssembly.Table,
     runtimeReady: boolean,
+    disableManagedTransition: boolean,
     monoThreadInfo: PThreadInfo,
     proxyGCHandle: GCHandle | undefined,
     managedThreadTID: PThreadPtr,