tor-browser

commit a7c16b5d07d299e4e5fd3a2894f6e3f4e7e4c09b
parent 269a06ecd851689a6b6e73f46bcd8639868fc692
Author: Matthew Gaudet <mgaudet@mozilla.com>
Date:   Wed,  1 Oct 2025 21:38:52 +0000

Bug 1983154 - Select debugger queue where required r=arai,smaug,dom-worker-reviewers,asuth

I don't love having a virtual dispatch on this hot path, but this is required for matching
existing semantics, as revealed by  dom/workers/test/test_WorkerDebugger_promise.xhtml

Longer term I'd love to do something else.

Differential Revision: https://phabricator.services.mozilla.com/D264131

Diffstat:
M
dom/workers/RuntimeService.cpp
 | 
6
++++++
M
js/public/Promise.h
 | 
8
++++++++
M
js/src/builtin/Promise.cpp
 | 
20
++++++++++++++------
M
xpcom/base/CycleCollectedJSContext.cpp
 | 
3
---

4 files changed, 28 insertions(+), 9 deletions(-)
diff --git a/dom/workers/RuntimeService.cpp b/dom/workers/RuntimeService.cpp
@@ -983,6 +983,12 @@ class WorkerJSContext final : public mozilla::CycleCollectedJSContext {
     return NS_OK;
   }
 
+  virtual bool useDebugQueue(JS::Handle<JSObject*> global) const override {
+    MOZ_ASSERT(!NS_IsMainThread());
+
+    return !(IsWorkerGlobal(global) || IsShadowRealmGlobal(global));
+  }
+
   virtual void DispatchToMicroTask(
       already_AddRefed<MicroTaskRunnable> aRunnable) override {
     RefPtr<MicroTaskRunnable> runnable(aRunnable);
diff --git a/js/public/Promise.h b/js/public/Promise.h
@@ -113,6 +113,14 @@ class JS_PUBLIC_API JobQueue {
    */
   virtual bool isDrainingStopped() const = 0;
 
+  /*
+   * When enqueueing a job, should the job be enqueued in the debug queue
+   * rather than the regular queue?
+   */
+  virtual bool useDebugQueue(JS::Handle<JSObject*> global) const {
+    return false;
+  }
+
  protected:
   friend class AutoDebuggerJobQueueInterruption;
 
diff --git a/js/src/builtin/Promise.cpp b/js/src/builtin/Promise.cpp
@@ -1677,6 +1677,17 @@ static bool ResolvePromiseFunction(JSContext* cx, unsigned argc, Value* vp) {
   return true;
 }
 
+static bool EnqueueJob(JSContext* cx, JS::MicroTask&& job) {
+  MOZ_ASSERT(cx->realm());
+
+  // Only check if we need to use the debug queue when we're not on main thread.
+  if (MOZ_UNLIKELY(!cx->runtime()->isMainRuntime() &&
+                   cx->jobQueue->useDebugQueue(cx->global()))) {
+    return cx->microTaskQueues->enqueueDebugMicroTask(cx, std::move(job));
+  }
+  return cx->microTaskQueues->enqueueRegularMicroTask(cx, std::move(job));
+}
+
 static bool PromiseReactionJob(JSContext* cx, unsigned argc, Value* vp);
 
 /**
@@ -1902,8 +1913,7 @@ static bool PromiseReactionJob(JSContext* cx, unsigned argc, Value* vp);
     }
 
     // HostEnqueuePromiseJob(job.[[Job]], job.[[Realm]]).
-    return cx->microTaskQueues->enqueueRegularMicroTask(
-        cx, std::move(reactionVal.get()));
+    return EnqueueJob(cx, std::move(reactionVal.get()));
   }
 
   RootedField<JSObject*, 7> hostDefinedData(roots);
@@ -2920,8 +2930,7 @@ static bool PromiseResolveBuiltinThenableJob(JSContext* cx, unsigned argc,
 
     thenableJob->setHostDefinedGlobalRepresentative(
         hostDefinedGlobalRepresentative);
-    return cx->microTaskQueues->enqueueRegularMicroTask(
-        cx, ObjectValue(*thenableJob));
+    return EnqueueJob(cx, ObjectValue(*thenableJob));
   }
 
   // Step 1. Let job be a new Job Abstract Closure with no parameters that
@@ -2981,8 +2990,7 @@ static bool PromiseResolveBuiltinThenableJob(JSContext* cx, unsigned argc,
       return false;
     }
 
-    return cx->microTaskQueues->enqueueRegularMicroTask(
-        cx, ObjectValue(*thenableJob));
+    return EnqueueJob(cx, ObjectValue(*thenableJob));
   }
 
   // Step 1. Let job be a new Job Abstract Closure with no parameters that
diff --git a/xpcom/base/CycleCollectedJSContext.cpp b/xpcom/base/CycleCollectedJSContext.cpp
@@ -1284,10 +1284,7 @@ void CycleCollectedJSContext::PerformDebuggerMicroTaskCheckpoint() {
   // this method is supposed to know what they are doing.
 
   JSContext* cx = Context();
-
   if (StaticPrefs::javascript_options_use_js_microtask_queue()) {
-    MOZ_ASSERT(GetDebuggerMicroTaskQueue().empty());
-
     while (JS::HasDebuggerMicroTasks(cx)) {
       MOZ_ASSERT(mDebuggerMicroTaskQueue.empty());
       MOZ_ASSERT(mPendingMicroTaskRunnables.empty());