Concurrency: Isolate global executor installation by MainActor

Author: kateinoigakukun

Sources/JavaScriptEventLoop/JavaScriptEventLoop.swift

@@ -102,14 +102,14 @@ public final class JavaScriptEventLoop: SerialExecutor, @unchecked Sendable {
         return eventLoop
     }
 
-    private static var didInstallGlobalExecutor = false
+    @MainActor private static var didInstallGlobalExecutor = false
 
     /// Set JavaScript event loop based executor to be the global executor
     /// Note that this should be called before any of the jobs are created.
     /// This installation step will be unnecessary after custom executor are
     /// introduced officially. See also [a draft proposal for custom 
     /// executors](https://github.com/rjmccall/swift-evolution/blob/custom-executors/proposals/0000-custom-executors.md#the-default-global-concurrent-executor)
-    public static func installGlobalExecutor() {
+    @MainActor public static func installGlobalExecutor() {
         guard !didInstallGlobalExecutor else { return }
 
         #if compiler(>=5.9)

Sources/JavaScriptEventLoop/WebWorkerTaskExecutor.swift

@@ -426,14 +426,15 @@ public final class WebWorkerTaskExecutor: TaskExecutor {
 
     // MARK: Global Executor hack
 
-    private static var _mainThread: pthread_t?
-    private static var _swift_task_enqueueGlobal_hook_original: UnsafeMutableRawPointer?
-    private static var _swift_task_enqueueGlobalWithDelay_hook_original: UnsafeMutableRawPointer?
-    private static var _swift_task_enqueueGlobalWithDeadline_hook_original: UnsafeMutableRawPointer?
+    @MainActor private static var _mainThread: pthread_t?
+    @MainActor private static var _swift_task_enqueueGlobal_hook_original: UnsafeMutableRawPointer?
+    @MainActor private static var _swift_task_enqueueGlobalWithDelay_hook_original: UnsafeMutableRawPointer?
+    @MainActor private static var _swift_task_enqueueGlobalWithDeadline_hook_original: UnsafeMutableRawPointer?
 
     /// Install a global executor that forwards jobs from Web Worker threads to the main thread.
     ///
     /// This function must be called once before using the Web Worker task executor.
+    @MainActor
     public static func installGlobalExecutor() {
         #if canImport(wasi_pthread) && compiler(>=6.1) && _runtime(_multithreaded)
         // Ensure this function is called only once.

Sources/JavaScriptEventLoopTestSupport/JavaScriptEventLoopTestSupport.swift

@@ -25,7 +25,9 @@ import JavaScriptEventLoop
 @available(macOS 14.0, iOS 17.0, watchOS 10.0, tvOS 17.0, *)
 @_cdecl("swift_javascriptkit_activate_js_executor_impl")
 func swift_javascriptkit_activate_js_executor_impl() {
-    JavaScriptEventLoop.installGlobalExecutor()
+    MainActor.assumeIsolated {
+        JavaScriptEventLoop.installGlobalExecutor()
+    }
 }
 
 #endif

Sources/_CJavaScriptEventLoop/include/_CJavaScriptEventLoop.h

@@ -9,6 +9,8 @@
 
 #define SWIFT_EXPORT_FROM(LIBRARY) __attribute__((__visibility__("default")))
 
+#define SWIFT_NONISOLATED_UNSAFE __attribute__((swift_attr("nonisolated(unsafe)")))
+
 /// A schedulable unit
 /// Note that this type layout is a part of public ABI, so we expect this field layout won't break in the future versions.
 /// Current implementation refers the `swift-5.5-RELEASE` implementation.
@@ -27,13 +29,13 @@ typedef SWIFT_CC(swift) void (*swift_task_enqueueGlobal_original)(
     Job *_Nonnull job);
 
 SWIFT_EXPORT_FROM(swift_Concurrency)
-extern void *_Nullable swift_task_enqueueGlobal_hook;
+extern void *_Nullable swift_task_enqueueGlobal_hook SWIFT_NONISOLATED_UNSAFE;
 
 /// A hook to take over global enqueuing with delay.
 typedef SWIFT_CC(swift) void (*swift_task_enqueueGlobalWithDelay_original)(
     unsigned long long delay, Job *_Nonnull job);
 SWIFT_EXPORT_FROM(swift_Concurrency)
-extern void *_Nullable swift_task_enqueueGlobalWithDelay_hook;
+extern void *_Nullable swift_task_enqueueGlobalWithDelay_hook SWIFT_NONISOLATED_UNSAFE;
 
 typedef SWIFT_CC(swift) void (*swift_task_enqueueGlobalWithDeadline_original)(
     long long sec,
@@ -42,13 +44,13 @@ typedef SWIFT_CC(swift) void (*swift_task_enqueueGlobalWithDeadline_original)(
     long long tnsec,
     int clock, Job *_Nonnull job);
 SWIFT_EXPORT_FROM(swift_Concurrency)
-extern void *_Nullable swift_task_enqueueGlobalWithDeadline_hook;
+extern void *_Nullable swift_task_enqueueGlobalWithDeadline_hook SWIFT_NONISOLATED_UNSAFE;
 
 /// A hook to take over main executor enqueueing.
 typedef SWIFT_CC(swift) void (*swift_task_enqueueMainExecutor_original)(
     Job *_Nonnull job);
 SWIFT_EXPORT_FROM(swift_Concurrency)
-extern void *_Nullable swift_task_enqueueMainExecutor_hook;
+extern void *_Nullable swift_task_enqueueMainExecutor_hook SWIFT_NONISOLATED_UNSAFE;
 
 /// A hook to override the entrypoint to the main runloop used to drive the
 /// concurrency runtime and drain the main queue. This function must not return.
@@ -59,13 +61,13 @@ typedef SWIFT_CC(swift) void (*swift_task_asyncMainDrainQueue_original)();
 typedef SWIFT_CC(swift) void (*swift_task_asyncMainDrainQueue_override)(
     swift_task_asyncMainDrainQueue_original _Nullable original);
 SWIFT_EXPORT_FROM(swift_Concurrency)
-extern void *_Nullable swift_task_asyncMainDrainQueue_hook;
+extern void *_Nullable swift_task_asyncMainDrainQueue_hook SWIFT_NONISOLATED_UNSAFE;
 
 
 /// MARK: - thread local storage
 
 extern _Thread_local void * _Nullable swjs_thread_local_event_loop;
 
-extern _Thread_local void * _Nullable swjs_thread_local_task_executor_worker;
+extern _Thread_local void * _Nullable swjs_thread_local_task_executor_worker SWIFT_NONISOLATED_UNSAFE;
 
 #endif