[K/N][Runtime] Add a lock method to thread registry

kotlin-native/runtime/src/gc/common/cpp/MarkAndSweepUtils.hpp

@@ -53,7 +53,7 @@ template <typename Traits>
 typename Traits::ObjectFactory::FinalizerQueue Sweep(typename Traits::ObjectFactory& objectFactory) noexcept {
     typename Traits::ObjectFactory::FinalizerQueue finalizerQueue;
 
-    auto iter = objectFactory.Iter();
+    auto iter = objectFactory.LockForIter();
     for (auto it = iter.begin(); it != iter.end();) {
         if (Traits::TryResetMark(*it)) {
             ++it;

kotlin-native/runtime/src/gc/common/cpp/MarkAndSweepUtilsSweepTest.cpp

@@ -175,7 +175,7 @@ public:
         testing::Mock::VerifyAndClear(&finalizerHook());
         // TODO: Figure out a better way to clear up the stuff.
         EXPECT_CALL(finalizerHook(), Call(testing::_)).Times(testing::AnyNumber());
-        for (auto node : objectFactory_.Iter()) {
+        for (auto node : objectFactory_.LockForIter()) {
             auto* obj = node->IsArray() ? node->GetArrayHeader()->obj() : node->GetObjHeader();
             if (auto* extraObject = mm::ExtraObjectData::Get(obj)) {
                 extraObject->ClearWeakReferenceCounter();
@@ -196,7 +196,7 @@ public:
 
     KStdVector<ObjHeader*> Alive() {
         KStdVector<ObjHeader*> objects;
-        for (auto node : objectFactory_.Iter()) {
+        for (auto node : objectFactory_.LockForIter()) {
             objects.push_back(node.IsArray() ? node.GetArrayHeader()->obj() : node.GetObjHeader());
         }
         return objects;

kotlin-native/runtime/src/gc/stms/cpp/SameThreadMarkAndSweep.cpp

@@ -126,7 +126,7 @@ mm::ObjectFactory<gc::SameThreadMarkAndSweep>::FinalizerQueue gc::SameThreadMark
     }
 
     KStdVector<ObjHeader*> graySet;
-    for (auto& thread : mm::GlobalData::Instance().threadRegistry().Iter()) {
+    for (auto& thread : mm::GlobalData::Instance().threadRegistry().LockForIter()) {
         // TODO: Maybe it's more efficient to do by the suspending thread?
         thread.Publish();
         for (auto* object : mm::ThreadRootSet(thread)) {

kotlin-native/runtime/src/gc/stms/cpp/SameThreadMarkAndSweepTest.cpp

@@ -191,7 +191,7 @@ KStdVector<ObjHeader*> Alive(mm::ThreadData& threadData) {
     for (auto node : threadData.objectFactoryThreadQueue()) {
         objects.push_back(node.IsArray() ? node.GetArrayHeader()->obj() : node.GetObjHeader());
     }
-    for (auto node : mm::GlobalData::Instance().objectFactory().Iter()) {
+    for (auto node : mm::GlobalData::Instance().objectFactory().LockForIter()) {
         objects.push_back(node.IsArray() ? node.GetArrayHeader()->obj() : node.GetObjHeader());
     }
     return objects;

kotlin-native/runtime/src/main/cpp/MultiSourceQueue.hpp

@@ -119,7 +119,7 @@ public:
 
     // Lock `MultiSourceQueue` for safe iteration. If element was scheduled for deletion,
     // it'll still be iterated. Use `ApplyDeletions` to remove those elements.
-    Iterable Iter() noexcept { return Iterable(*this); }
+    Iterable LockForIter() noexcept { return Iterable(*this); }
 
     // Lock `MultiSourceQueue` and apply deletions. Only deletes elements that were published.
     void ApplyDeletions() noexcept {

kotlin-native/runtime/src/main/cpp/MultiSourceQueueTest.cpp

@@ -21,7 +21,7 @@ namespace {
 template <typename T>
 KStdVector<T> Collect(MultiSourceQueue<T>& queue) {
     KStdVector<T> result;
-    for (const auto& element : queue.Iter()) {
+    for (const auto& element : queue.LockForIter()) {
         result.push_back(element);
     }
     return result;
@@ -254,7 +254,7 @@ TEST(MultiSourceQueueTest, IterWhileConcurrentPublish) {
 
     KStdVector<int> actualBefore;
     {
-        auto iter = queue.Iter();
+        auto iter = queue.LockForIter();
         while (readyCount < kThreadCount) {
         }
         canStart = true;

kotlin-native/runtime/src/main/cpp/SingleLockList.hpp

@@ -71,7 +71,7 @@ public:
 
     class Iterable : private MoveOnly {
     public:
-        explicit Iterable(SingleLockList* list) noexcept : list_(list), guard_(list->mutex_) {}
+        explicit Iterable(SingleLockList* list) noexcept : list_(list), guard_(list->Lock()) {}
 
         Iterator begin() noexcept { return Iterator(list_->root_.get()); }
 
@@ -136,12 +136,14 @@ public:
 
     // Returned value locks `this` to perform safe iteration. `this` unlocks when
     // `Iterable` gets out of scope. Example usage:
-    // for (auto& value: list.Iter()) {
+    // for (auto& value: list.LockForIter()) {
     //    // Do something with `value`, there's a guarantee that it'll not be
     //    // destroyed mid-iteration.
     // }
     // // At this point `list` is unlocked.
-    Iterable Iter() noexcept { return Iterable(this); }
+    Iterable LockForIter() noexcept { return Iterable(this); }
+
+    std::unique_lock<Mutex> Lock() noexcept { return std::unique_lock(mutex_); }
 
 private:
     // Expects `mutex_` to be held by the current thread.

kotlin-native/runtime/src/main/cpp/SingleLockListTest.cpp

@@ -49,7 +49,7 @@ TEST(SingleLockListTest, EmplaceAndIter) {
     list.Emplace(kThird);
 
     KStdVector<int> actual;
-    for (int element : list.Iter()) {
+    for (int element : list.LockForIter()) {
         actual.push_back(element);
     }
 
@@ -67,7 +67,7 @@ TEST(SingleLockListTest, EmplaceEraseAndIter) {
     list.Erase(secondNode);
 
     KStdVector<int> actual;
-    for (int element : list.Iter()) {
+    for (int element : list.LockForIter()) {
         actual.push_back(element);
     }
 
@@ -78,7 +78,7 @@ TEST(SingleLockListTest, IterEmpty) {
     IntList list;
 
     KStdVector<int> actual;
-    for (int element : list.Iter()) {
+    for (int element : list.LockForIter()) {
         actual.push_back(element);
     }
 
@@ -99,7 +99,7 @@ TEST(SingleLockListTest, EraseToEmptyEmplaceAndIter) {
     list.Emplace(kFourth);
 
     KStdVector<int> actual;
-    for (int element : list.Iter()) {
+    for (int element : list.LockForIter()) {
         actual.push_back(element);
     }
 
@@ -131,7 +131,7 @@ TEST(SingleLockListTest, ConcurrentEmplace) {
     }
 
     KStdVector<int> actual;
-    for (int element : list.Iter()) {
+    for (int element : list.LockForIter()) {
         actual.push_back(element);
     }
 
@@ -166,7 +166,7 @@ TEST(SingleLockListTest, ConcurrentErase) {
     }
 
     KStdVector<int> actual;
-    for (int element : list.Iter()) {
+    for (int element : list.LockForIter()) {
         actual.push_back(element);
     }
 
@@ -202,7 +202,7 @@ TEST(SingleLockListTest, IterWhileConcurrentEmplace) {
 
     KStdVector<int> actualBefore;
     {
-        auto iter = list.Iter();
+        auto iter = list.LockForIter();
         canStart = true;
         while (startedCount < kThreadCount) {
         }
@@ -219,7 +219,7 @@ TEST(SingleLockListTest, IterWhileConcurrentEmplace) {
     EXPECT_THAT(actualBefore, testing::ElementsAreArray(expectedBefore));
 
     KStdVector<int> actualAfter;
-    for (int element : list.Iter()) {
+    for (int element : list.LockForIter()) {
         actualAfter.push_back(element);
     }
 
@@ -251,7 +251,7 @@ TEST(SingleLockListTest, IterWhileConcurrentErase) {
 
     KStdVector<int> actualBefore;
     {
-        auto iter = list.Iter();
+        auto iter = list.LockForIter();
         canStart = true;
         while (startedCount < kThreadCount) {
         }
@@ -268,13 +268,99 @@ TEST(SingleLockListTest, IterWhileConcurrentErase) {
     EXPECT_THAT(actualBefore, testing::ElementsAreArray(expectedBefore));
 
     KStdVector<int> actualAfter;
-    for (int element : list.Iter()) {
+    for (int element : list.LockForIter()) {
         actualAfter.push_back(element);
     }
 
     EXPECT_THAT(actualAfter, testing::IsEmpty());
 }
 
+TEST(SingleLockListTest, LockAndEmplace) {
+    SingleLockList<int, std::recursive_mutex> list;
+    constexpr int kThreadCount = kDefaultThreadCount;
+
+    KStdVector<std::thread> threads;
+    KStdVector<int> actualLocked;
+    KStdVector<int> actualUnlocked;
+    KStdVector<int> expectedUnlocked;
+    for (int i = 0; i < kThreadCount; i++) {
+        expectedUnlocked.push_back(i);
+    }
+    std::atomic<int> startedCount(0);
+    {
+        std::unique_lock lock = list.Lock();
+        for (int i = 0; i < kThreadCount; i++) {
+            threads.emplace_back([&startedCount, &list, i]() {
+                startedCount++;
+                list.Emplace(i);
+            });
+        }
+        while (startedCount != kThreadCount) {
+            std::this_thread::yield();
+        }
+        // Here still may be a race leading to false-successful EXPECT
+        // if the scheduler suspend all threads right before list.Emplace.
+        // But this situation looks unlikely
+        for (int element : list.LockForIter()) {
+            actualLocked.push_back(element);
+        }
+    }
+
+    for (auto& thread : threads) {
+        thread.join();
+    }
+    for (int element : list.LockForIter()) {
+        actualUnlocked.push_back(element);
+    }
+    EXPECT_THAT(actualLocked, testing::IsEmpty());
+    EXPECT_THAT(actualUnlocked, testing::UnorderedElementsAreArray(expectedUnlocked));
+}
+
+TEST(SingleLockListTest, LockAndErase) {
+    SingleLockList<int, std::recursive_mutex> list;
+    constexpr int kThreadCount = kDefaultThreadCount;
+
+    KStdVector<SingleLockList<int, std::recursive_mutex>::Node*> items;
+    KStdVector<int> expectedLocked;
+    KStdVector<std::thread> threads;
+    KStdVector<int> actualLocked;
+    KStdVector<int> actualUnlocked;
+    std::atomic<int> startedCount(0);
+
+    for (int i = 0; i < kThreadCount; i++) {
+        expectedLocked.push_back(i);
+        items.push_back(list.Emplace(i));
+    }
+    {
+        std::unique_lock lock = list.Lock();
+        for (int i = 0; i < kThreadCount; i++) {
+            threads.emplace_back([&startedCount, &list, &items, i]() {
+                startedCount++;
+                list.Erase(items[i]);
+            });
+        }
+        while (startedCount != kThreadCount) {
+            std::this_thread::yield();
+        }
+        // Here still may be a race leading to false-successful EXPECT
+        // if the scheduler suspend all threads right before list.Erase.
+        // But this situation looks unlikely
+        for (int element : list.LockForIter()) {
+            actualLocked.push_back(element);
+        }
+    }
+
+    for (auto& thread : threads) {
+        thread.join();
+    }
+    for (int element : list.LockForIter()) {
+        actualUnlocked.push_back(element);
+    }
+
+    EXPECT_THAT(actualLocked, testing::UnorderedElementsAreArray(expectedLocked));
+    EXPECT_THAT(actualUnlocked, testing::IsEmpty());
+}
+
 namespace {
 
 class PinnedType : private Pinned {
@@ -300,7 +386,7 @@ TEST(SingleLockListTest, PinnedType) {
     list.Erase(itemNode);
 
     KStdVector<PinnedType*> actualAfter;
-    for (auto& element : list.Iter()) {
+    for (auto& element : list.LockForIter()) {
         actualAfter.push_back(&element);
     }
 

kotlin-native/runtime/src/mm/cpp/ExceptionObjHolderTest.cpp

@@ -24,7 +24,7 @@ public:
         stableRefs.ProcessThread(&threadData);
         stableRefs.ProcessDeletions();
         KStdVector<ObjHeader*> result;
-        for (const auto& obj : stableRefs.Iter()) {
+        for (const auto& obj : stableRefs.LockForIter()) {
             result.push_back(obj);
         }
         return result;

kotlin-native/runtime/src/mm/cpp/GlobalsRegistry.hpp

@@ -41,7 +41,7 @@ public:
     // TODO: Iteration over `globals_` will be slow, because it's `KStdList` collected at different times from
     // different threads, and so the nodes are all over the memory. Use metrics to understand how
     // much of a problem is it.
-    Iterable Iter() noexcept { return globals_.Iter(); }
+    Iterable LockForIter() noexcept { return globals_.LockForIter(); }
 
     void ClearForTests() { globals_.ClearForTests(); }
 

kotlin-native/runtime/src/mm/cpp/ObjectFactory.hpp

@@ -324,7 +324,7 @@ public:
     }
 
     // Lock `ObjectFactoryStorage` for safe iteration.
-    Iterable Iter() noexcept { return Iterable(*this); }
+    Iterable LockForIter() noexcept { return Iterable(*this); }
 
     void ClearForTests() {
         root_.reset();
@@ -619,7 +619,7 @@ public:
 
     class Iterable {
     public:
-        Iterable(ObjectFactory& owner) noexcept : iter_(owner.storage_.Iter()) {}
+        Iterable(ObjectFactory& owner) noexcept : iter_(owner.storage_.LockForIter()) {}
 
         Iterator begin() noexcept { return Iterator(iter_.begin()); }
         Iterator end() noexcept { return Iterator(iter_.end()); }
@@ -637,7 +637,8 @@ public:
     ObjectFactory() noexcept = default;
     ~ObjectFactory() = default;
 
-    Iterable Iter() noexcept { return Iterable(*this); }
+    // Lock ObjectFactory for safe iteration.
+    Iterable LockForIter() noexcept { return Iterable(*this); }
 
     void ClearForTests() { storage_.ClearForTests(); }
 

kotlin-native/runtime/src/mm/cpp/ObjectFactoryTest.cpp

@@ -39,7 +39,7 @@ using Consumer = typename Storage::Consumer;
 template <size_t DataAlignment>
 KStdVector<void*> Collect(ObjectFactoryStorage<DataAlignment>& storage) {
     KStdVector<void*> result;
-    for (auto& node : storage.Iter()) {
+    for (auto& node : storage.LockForIter()) {
         result.push_back(node.Data());
     }
     return result;
@@ -48,7 +48,7 @@ KStdVector<void*> Collect(ObjectFactoryStorage<DataAlignment>& storage) {
 template <typename T, size_t DataAlignment>
 KStdVector<T> Collect(ObjectFactoryStorage<DataAlignment>& storage) {
     KStdVector<T> result;
-    for (auto& node : storage.Iter()) {
+    for (auto& node : storage.LockForIter()) {
         result.push_back(*static_cast<T*>(node.Data()));
     }
     return result;
@@ -137,7 +137,7 @@ TEST(ObjectFactoryStorageTest, PublishDifferentTypes) {
 
     producer.Publish();
 
-    auto actual = storage.Iter();
+    auto actual = storage.LockForIter();
     auto it = actual.begin();
     EXPECT_THAT(it->Data<int>(), 1);
     ++it;
@@ -222,7 +222,7 @@ TEST(ObjectFactoryStorageTest, EraseFirst) {
     producer.Publish();
 
     {
-        auto iter = storage.Iter();
+        auto iter = storage.LockForIter();
         for (auto it = iter.begin(); it != iter.end();) {
             if (it->Data<int>() == 1) {
                 iter.EraseAndAdvance(it);
@@ -248,7 +248,7 @@ TEST(ObjectFactoryStorageTest, EraseMiddle) {
     producer.Publish();
 
     {
-        auto iter = storage.Iter();
+        auto iter = storage.LockForIter();
         for (auto it = iter.begin(); it != iter.end();) {
             if (it->Data<int>() == 2) {
                 iter.EraseAndAdvance(it);
@@ -274,7 +274,7 @@ TEST(ObjectFactoryStorageTest, EraseLast) {
     producer.Publish();
 
     {
-        auto iter = storage.Iter();
+        auto iter = storage.LockForIter();
         for (auto it = iter.begin(); it != iter.end();) {
             if (it->Data<int>() == 3) {
                 iter.EraseAndAdvance(it);
@@ -300,7 +300,7 @@ TEST(ObjectFactoryStorageTest, EraseAll) {
     producer.Publish();
 
     {
-        auto iter = storage.Iter();
+        auto iter = storage.LockForIter();
         for (auto it = iter.begin(); it != iter.end();) {
             iter.EraseAndAdvance(it);
         }
@@ -320,7 +320,7 @@ TEST(ObjectFactoryStorageTest, EraseTheOnlyElement) {
     producer.Publish();
 
     {
-        auto iter = storage.Iter();
+        auto iter = storage.LockForIter();
         auto it = iter.begin();
         iter.EraseAndAdvance(it);
         EXPECT_THAT(it, iter.end());
@@ -343,7 +343,7 @@ TEST(ObjectFactoryStorageTest, MoveFirst) {
     producer.Publish();
 
     {
-        auto iter = storage.Iter();
+        auto iter = storage.LockForIter();
         for (auto it = iter.begin(); it != iter.end();) {
             if (it->Data<int>() == 1) {
                 iter.MoveAndAdvance(consumer, it);
@@ -372,7 +372,7 @@ TEST(ObjectFactoryStorageTest, MoveMiddle) {
     producer.Publish();
 
     {
-        auto iter = storage.Iter();
+        auto iter = storage.LockForIter();
         for (auto it = iter.begin(); it != iter.end();) {
             if (it->Data<int>() == 2) {
                 iter.MoveAndAdvance(consumer, it);
@@ -401,7 +401,7 @@ TEST(ObjectFactoryStorageTest, MoveLast) {
     producer.Publish();
 
     {
-        auto iter = storage.Iter();
+        auto iter = storage.LockForIter();
         for (auto it = iter.begin(); it != iter.end();) {
             if (it->Data<int>() == 3) {
                 iter.MoveAndAdvance(consumer, it);
@@ -430,7 +430,7 @@ TEST(ObjectFactoryStorageTest, MoveAll) {
     producer.Publish();
 
     {
-        auto iter = storage.Iter();
+        auto iter = storage.LockForIter();
         for (auto it = iter.begin(); it != iter.end();) {
             iter.MoveAndAdvance(consumer, it);
         }
@@ -453,7 +453,7 @@ TEST(ObjectFactoryStorageTest, MoveTheOnlyElement) {
     producer.Publish();
 
     {
-        auto iter = storage.Iter();
+        auto iter = storage.LockForIter();
         auto it = iter.begin();
         iter.MoveAndAdvance(consumer, it);
         EXPECT_THAT(it, iter.end());
@@ -484,7 +484,7 @@ TEST(ObjectFactoryStorageTest, MoveAndErase) {
     producer.Publish();
 
     {
-        auto iter = storage.Iter();
+        auto iter = storage.LockForIter();
         for (auto it = iter.begin(); it != iter.end();) {
             ++it;
             iter.EraseAndAdvance(it);
@@ -566,7 +566,7 @@ TEST(ObjectFactoryStorageTest, IterWhileConcurrentPublish) {
 
     KStdVector<int> actualBefore;
     {
-        auto iter = storage.Iter();
+        auto iter = storage.LockForIter();
         while (readyCount < kThreadCount) {
         }
         canStart = true;
@@ -624,7 +624,7 @@ TEST(ObjectFactoryStorageTest, EraseWhileConcurrentPublish) {
     }
 
     {
-        auto iter = storage.Iter();
+        auto iter = storage.LockForIter();
         while (readyCount < kThreadCount) {
         }
         canStart = true;
@@ -772,7 +772,7 @@ TEST(ObjectFactoryTest, CreateObject) {
     EXPECT_THAT(node.GetObjHeader(), object);
     EXPECT_THAT(node.GCObjectData().flags, 42);
 
-    auto iter = objectFactory.Iter();
+    auto iter = objectFactory.LockForIter();
     auto it = iter.begin();
     EXPECT_THAT(*it, node);
     ++it;
@@ -792,7 +792,7 @@ TEST(ObjectFactoryTest, CreateObjectArray) {
     EXPECT_THAT(node.GetArrayHeader(), array);
     EXPECT_THAT(node.GCObjectData().flags, 42);
 
-    auto iter = objectFactory.Iter();
+    auto iter = objectFactory.LockForIter();
     auto it = iter.begin();
     EXPECT_THAT(*it, node);
     ++it;
@@ -812,7 +812,7 @@ TEST(ObjectFactoryTest, CreateCharArray) {
     EXPECT_THAT(node.GetArrayHeader(), array);
     EXPECT_THAT(node.GCObjectData().flags, 42);
 
-    auto iter = objectFactory.Iter();
+    auto iter = objectFactory.LockForIter();
     auto it = iter.begin();
     EXPECT_THAT(*it, node);
     ++it;
@@ -833,7 +833,7 @@ TEST(ObjectFactoryTest, Erase) {
     threadQueue.Publish();
 
     {
-        auto iter = objectFactory.Iter();
+        auto iter = objectFactory.LockForIter();
         for (auto it = iter.begin(); it != iter.end();) {
             if (it->IsArray()) {
                 iter.EraseAndAdvance(it);
@@ -844,7 +844,7 @@ TEST(ObjectFactoryTest, Erase) {
     }
 
     {
-        auto iter = objectFactory.Iter();
+        auto iter = objectFactory.LockForIter();
         int count = 0;
         for (auto it = iter.begin(); it != iter.end(); ++it, ++count) {
             EXPECT_FALSE(it->IsArray());
@@ -868,7 +868,7 @@ TEST(ObjectFactoryTest, Move) {
     threadQueue.Publish();
 
     {
-        auto iter = objectFactory.Iter();
+        auto iter = objectFactory.LockForIter();
         for (auto it = iter.begin(); it != iter.end();) {
             if (it->IsArray()) {
                 iter.MoveAndAdvance(finalizerQueue, it);
@@ -879,7 +879,7 @@ TEST(ObjectFactoryTest, Move) {
     }
 
     {
-        auto iter = objectFactory.Iter();
+        auto iter = objectFactory.LockForIter();
         int count = 0;
         for (auto it = iter.begin(); it != iter.end(); ++it, ++count) {
             EXPECT_FALSE(it->IsArray());
@@ -914,7 +914,7 @@ TEST(ObjectFactoryTest, RunFinalizers) {
     threadQueue.Publish();
 
     {
-        auto iter = objectFactory.Iter();
+        auto iter = objectFactory.LockForIter();
         for (auto it = iter.begin(); it != iter.end();) {
             iter.MoveAndAdvance(finalizerQueue, it);
         }
@@ -961,7 +961,7 @@ TEST(ObjectFactoryTest, ConcurrentPublish) {
         t.join();
     }
 
-    auto iter = objectFactory.Iter();
+    auto iter = objectFactory.LockForIter();
     KStdVector<ObjHeader*> actual;
     for (auto it = iter.begin(); it != iter.end(); ++it) {
         actual.push_back(it->GetObjHeader());

kotlin-native/runtime/src/mm/cpp/RootSet.hpp

@@ -104,7 +104,7 @@ public:
     };
 
     GlobalRootSet(GlobalsRegistry& globalsRegistry, StableRefRegistry& stableRefRegistry) noexcept :
-        globalsIterable_(globalsRegistry.Iter()), stableRefsIterable_(stableRefRegistry.Iter()) {}
+        globalsIterable_(globalsRegistry.LockForIter()), stableRefsIterable_(stableRefRegistry.LockForIter()) {}
     GlobalRootSet() noexcept;
 
     Iterator begin() noexcept { return Iterator(Iterator::begin, *this); }

kotlin-native/runtime/src/mm/cpp/StableRefRegistry.hpp

@@ -39,14 +39,14 @@ public:
     // when it's asked by GC to stop.
     void ProcessThread(mm::ThreadData* threadData) noexcept;
 
-    // Lock registry and apply deletions. Should be called on GC thread after all threads have published, and before `Iter`.
+    // Lock registry and apply deletions. Should be called on GC thread after all threads have published, and before `LockForIter`.
     void ProcessDeletions() noexcept;
 
     // Lock registry for safe iteration.
     // TODO: Iteration over `stableRefs_` will be slow, because it's `KStdList` collected at different times from
     // different threads, and so the nodes are all over the memory. Use metrics to understand how
     // much of a problem is it.
-    Iterable Iter() noexcept { return stableRefs_.Iter(); }
+    Iterable LockForIter() noexcept { return stableRefs_.LockForIter(); }
 
     void ClearForTests() noexcept { stableRefs_.ClearForTests(); }
 

kotlin-native/runtime/src/mm/cpp/TestSupport.cpp

@@ -44,10 +44,10 @@ std::vector<mm::ThreadData*> collect(mm::ThreadRegistry::Iterable& iterable) {
 
 extern "C" void Kotlin_TestSupport_AssertClearGlobalState() {
     // Validate that global registries are empty.
-    auto globals = mm::GlobalsRegistry::Instance().Iter();
-    auto objects = mm::GlobalData::Instance().objectFactory().Iter();
-    auto stableRefs = mm::StableRefRegistry::Instance().Iter();
-    auto threads = mm::ThreadRegistry::Instance().Iter();
+    auto globals = mm::GlobalsRegistry::Instance().LockForIter();
+    auto objects = mm::GlobalData::Instance().objectFactory().LockForIter();
+    auto stableRefs = mm::StableRefRegistry::Instance().LockForIter();
+    auto threads = mm::ThreadRegistry::Instance().LockForIter();
 
     EXPECT_THAT(collect<ObjHeader**>(globals), testing::UnorderedElementsAre());
     EXPECT_THAT(collect<mm::ObjectFactory<gc::GC>::NodeRef>(objects), testing::UnorderedElementsAre());

kotlin-native/runtime/src/mm/cpp/ThreadRegistry.cpp

@@ -31,8 +31,12 @@ void mm::ThreadRegistry::Unregister(Node* threadDataNode) noexcept {
     // Do not touch `currentThreadData_` as TLS may already have been deallocated.
 }
 
-mm::ThreadRegistry::Iterable mm::ThreadRegistry::Iter() noexcept {
-    return list_.Iter();
+mm::ThreadRegistry::Iterable mm::ThreadRegistry::LockForIter() noexcept {
+    return list_.LockForIter();
+}
+
+std::unique_lock<mm::ThreadRegistry::Mutex> mm::ThreadRegistry::Lock() noexcept {
+    return list_.Lock();
 }
 
 ALWAYS_INLINE mm::ThreadData* mm::ThreadRegistry::CurrentThreadData() const noexcept {

kotlin-native/runtime/src/mm/cpp/ThreadRegistry.hpp

@@ -19,8 +19,9 @@ class ThreadData;
 
 class ThreadRegistry final : private Pinned {
 public:
-    using Node = SingleLockList<ThreadData>::Node;
-    using Iterable = SingleLockList<ThreadData>::Iterable;
+    using Mutex = std::recursive_mutex;
+    using Node = SingleLockList<ThreadData, Mutex>::Node;
+    using Iterable = SingleLockList<ThreadData, Mutex>::Iterable;
 
     static ThreadRegistry& Instance() noexcept;
 
@@ -30,7 +31,9 @@ public:
     void Unregister(Node* threadDataNode) noexcept;
 
     // Locks `ThreadRegistry` for safe iteration.
-    Iterable Iter() noexcept;
+    Iterable LockForIter() noexcept;
+
+    std::unique_lock<Mutex> Lock() noexcept;
 
     // Try not to use these methods very often, as (1) thread local access can be slow on some platforms,
     // (2) TLS gets deallocated before our thread destruction hooks run.
@@ -51,7 +54,7 @@ private:
 
     static THREAD_LOCAL_VARIABLE Node* currentThreadDataNode_;
 
-    SingleLockList<ThreadData> list_;
+    SingleLockList<ThreadData, Mutex> list_;
 };
 
 } // namespace mm

kotlin-native/runtime/src/mm/cpp/ThreadSuspension.cpp

@@ -21,7 +21,7 @@ template<typename F>
 bool allThreads(F predicate) noexcept {
     auto& threadRegistry = kotlin::mm::ThreadRegistry::Instance();
     auto* currentThread = threadRegistry.CurrentThreadData();
-    kotlin::mm::ThreadRegistry::Iterable threads = kotlin::mm::ThreadRegistry::Instance().Iter();
+    kotlin::mm::ThreadRegistry::Iterable threads = kotlin::mm::ThreadRegistry::Instance().LockForIter();
     for (auto& thread : threads) {
         // Handle if suspension was initiated by the mutator thread.
         if (&thread == currentThread)

kotlin-native/runtime/src/mm/cpp/ThreadSuspensionTest.cpp

@@ -29,7 +29,7 @@ constexpr size_t kDefaultReportingStep = 1000;
 
 KStdVector<mm::ThreadData*> collectThreadData() {
     KStdVector<mm::ThreadData*> result;
-    auto iter = mm::ThreadRegistry::Instance().Iter();
+    auto iter = mm::ThreadRegistry::Instance().LockForIter();
     for (auto& thread : iter) {
         result.push_back(&thread);
     }