[JSC] Atomics.waitAsync should be invocable from the main thread

jjgriego · mikhailramalho · commit 9259434c0151 · 2023-01-12T15:24:14.000-08:00
https://bugs.webkit.org/show_bug.cgi?id=250518 Reviewed by Keith Miller. According to the current proposed spec [1], async atomic waits are not restricted to threads with `AgentCanSuspend()`--so, Atomics.waitAsync should not throw a TypeError for this reason. I've added a (very simple) test to this effect. So, we should delay the check for `isAtomicsWaitAllowedOnCurrentThread` until after we know the wait is known to be synchronous. If there's an implementation reason we shouldn't do this, let me know, but I couldn't find one. [1] https://tc39.es/proposal-atomics-wait-async/#sec-dowait * LayoutTests/js/Atomics-waitasync-invocable-on-main-thread-expected.txt: Added. * LayoutTests/js/Atomics-waitasync-invocable-on-main-thread.html: Added. * Source/JavaScriptCore/runtime/AtomicsObject.cpp: (JSC::atomicsWaitImpl): Canonical link: https://commits.webkit.org/258856@main
diff --git a/LayoutTests/js/Atomics-waitasync-invocable-on-main-thread-expected.txt b/LayoutTests/js/Atomics-waitasync-invocable-on-main-thread-expected.txt
@@ -0,0 +1,11 @@
+Test to ensure Atomics.waitAsync is invocable on the main thread
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS successfullyParsed is true
+
+TEST COMPLETE
+
+PASS Atomics.waitAsync can return immediately from the main thread
+
diff --git a/LayoutTests/js/Atomics-waitasync-invocable-on-main-thread.html b/LayoutTests/js/Atomics-waitasync-invocable-on-main-thread.html
@@ -0,0 +1,21 @@
+<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
+<html>
+    <head>
+        <script src="../resources/js-test-pre.js"></script>
+    </head>
+    <body>
+        <script src =../resources/testharness.js></script>
+        <script src =../resources/testharnessreport.js></script>
+        <script>
+        description("Test to ensure Atomics.waitAsync is invocable on the main thread");
+
+        promise_test(async t => {
+            const buffer = new SharedArrayBuffer(1024);
+            const array = new Int32Array(buffer);
+            await Atomics.waitAsync(array, 0, 1).value;
+        }, "Atomics.waitAsync can return immediately from the main thread");
+
+        </script>
+        <script src="../resources/js-test-post.js"></script>
+    </body>
+</html>
diff --git a/Source/JavaScriptCore/runtime/AtomicsObject.cpp b/Source/JavaScriptCore/runtime/AtomicsObject.cpp
@@ -449,15 +449,14 @@ JSValue atomicsWaitImpl(JSGlobalObject* globalObject, JSArrayType* typedArray, u
     if (!std::isnan(timeoutInMilliseconds))
         timeout = std::max(Seconds::fromMilliseconds(timeoutInMilliseconds), 0_s);
 
+    if (type == AtomicsWaitType::Async)
+        return WaiterListManager::singleton().waitAsync(globalObject, vm, ptr, expectedValue, timeout);
+
     if (!vm.m_typedArrayController->isAtomicsWaitAllowedOnCurrentThread()) {
-        throwTypeError(globalObject, scope, makeString("Atomics."_s,
-            (type == AtomicsWaitType::Async ? "waitAsync"_s : "wait"_s), " cannot be called from the current thread."_s));
+        throwTypeError(globalObject, scope, "Atomics.wait cannot be called from the current thread."_s);
         return { };
     }
 
-    if (type == AtomicsWaitType::Async)
-        return WaiterListManager::singleton().waitAsync(globalObject, vm, ptr, expectedValue, timeout);
-
     auto result = WaiterListManager::singleton().waitSync(vm, ptr, expectedValue, timeout);
     switch (result) {
     case WaiterListManager::WaitSyncResult::OK:
