tor-browser

commit c858cd0fdd613c8f96e27e275ff0186d80d97dd4
parent d76d0ab5ce6036611afde8d69571aee3b76420ac
Author: Matthew Gaudet <mgaudet@mozilla.com>
Date:   Thu,  6 Nov 2025 21:21:53 +0000

Bug 1997702 - Remove use of PersistentRooted on JSContext for MicroTaskQueues r=jonco

Differential Revision: https://phabricator.services.mozilla.com/D271502

Diffstat:
M
js/src/vm/JSContext.cpp
 | 
13
+++++++++----
M
js/src/vm/JSContext.h
 | 
5
+++--

2 files changed, 12 insertions(+), 6 deletions(-)
diff --git a/js/src/vm/JSContext.cpp b/js/src/vm/JSContext.cpp
@@ -1140,7 +1140,7 @@ JS_PUBLIC_API bool JS::HasDebuggerMicroTasks(JSContext* cx) {
 struct SavedMicroTaskQueueImpl : public JS::SavedMicroTaskQueue {
   explicit SavedMicroTaskQueueImpl(JSContext* cx) : savedQueues(cx) {
     savedQueues = js::MakeUnique<js::MicroTaskQueueSet>(cx);
-    std::swap(cx->microTaskQueues.get(), savedQueues.get());
+    std::swap(cx->microTaskQueues, savedQueues.get());
   }
   ~SavedMicroTaskQueueImpl() override = default;
   JS::PersistentRooted<js::UniquePtr<js::MicroTaskQueueSet>> savedQueues;
@@ -1163,7 +1163,7 @@ JS_PUBLIC_API void JS::RestoreMicroTaskQueue(
   // There's only one impl, so we know this is safe.
   SavedMicroTaskQueueImpl* savedQueueImpl =
       static_cast<SavedMicroTaskQueueImpl*>(savedQueue.get());
-  std::swap(savedQueueImpl->savedQueues.get(), cx->microTaskQueues.get());
+  std::swap(savedQueueImpl->savedQueues.get(), cx->microTaskQueues);
 }
 
 JS_PUBLIC_API size_t JS::GetRegularMicroTaskCount(JSContext* cx) {
@@ -1268,8 +1268,7 @@ JSContext::JSContext(JSRuntime* runtime, const JS::ContextOptions& options)
       canSkipEnqueuingJobs(this, false),
       promiseRejectionTrackerCallback(this, nullptr),
       promiseRejectionTrackerCallbackData(this, nullptr),
-      insideExclusiveDebuggerOnEval(this, nullptr),
-      microTaskQueues(this) {
+      insideExclusiveDebuggerOnEval(this, nullptr) {
   MOZ_ASSERT(static_cast<JS::RootingContext*>(this) ==
              JS::RootingContext::get(this));
 }
@@ -1525,6 +1524,12 @@ void JSContext::trace(JSTracer* trc) {
 #ifdef ENABLE_WASM_JSPI
   wasm().promiseIntegration.trace(trc);
 #endif
+
+  // Skip tracing the microtask queues on minor GC as we will be updating
+  // nursery pointers through the store buffer instead.
+  if (!trc->isTenuringTracer() && microTaskQueues) {
+    microTaskQueues->trace(trc);
+  }
 }
 
 JS::NativeStackLimit JSContext::stackLimitForJitCode(JS::StackKind kind) {
diff --git a/js/src/vm/JSContext.h b/js/src/vm/JSContext.h
@@ -158,7 +158,8 @@ enum class ShouldCaptureStack { Maybe, Always };
 // MG:XXX: It would be nice to explore the typical depth of the queue
 //         to see if we can get it all inline in the common case.
 // MG:XXX: This appears to be broken for non-zero values of inline!
-using MicroTaskQueue = js::TraceableFifo<JS::Value, 0, TempAllocPolicy>;
+using MicroTaskQueue =
+    js::TraceableFifo<js::HeapPtr<JS::Value>, 0, TempAllocPolicy>;
 
 // A pair of microtask queues; one debug and one 'regular' (non-debug).
 struct MicroTaskQueueSet {
@@ -1053,7 +1054,7 @@ struct JS_PUBLIC_API JSContext : public JS::RootingContext,
   bool hasExecutionTracer() { return false; }
 #endif
 
-  JS::PersistentRooted<js::UniquePtr<js::MicroTaskQueueSet>> microTaskQueues;
+  js::UniquePtr<js::MicroTaskQueueSet> microTaskQueues;
 }; /* struct JSContext */
 
 inline JSContext* JSRuntime::mainContextFromOwnThread() {