diff --git a/kotlin-native/runtime/src/main/cpp/CleanerTest.cpp b/kotlin-native/runtime/src/main/cpp/CleanerTest.cpp
index 4861b9b455f..ca36bcd109a 100644
--- a/kotlin-native/runtime/src/main/cpp/CleanerTest.cpp
+++ b/kotlin-native/runtime/src/main/cpp/CleanerTest.cpp
@@ -12,6 +12,7 @@
 #include "gtest/gtest.h"
 
 #include "Atomic.h"
+#include "TestSupport.hpp"
 #include "TestSupportCompilerGenerated.hpp"
 
 using testing::_;
@@ -21,7 +22,7 @@ using testing::_;
 TEST(CleanerTest, ConcurrentCreation) {
     ResetCleanerWorkerForTests();
 
-    constexpr int threadCount = 100;
+    constexpr int threadCount = kotlin::kDefaultThreadCount;
     constexpr KInt workerId = 42;
 
     auto createCleanerWorkerMock = ScopedCreateCleanerWorkerMock();
diff --git a/kotlin-native/runtime/src/main/cpp/MultiSourceQueue.hpp b/kotlin-native/runtime/src/main/cpp/MultiSourceQueue.hpp
index cafcf355dee..1a514855141 100644
--- a/kotlin-native/runtime/src/main/cpp/MultiSourceQueue.hpp
+++ b/kotlin-native/runtime/src/main/cpp/MultiSourceQueue.hpp
@@ -7,6 +7,9 @@
 #define RUNTIME_MULTI_SOURCE_QUEUE_H
 
 #include <list>
+#include <mutex>
+
+#include "Mutex.hpp"
 
 namespace kotlin {
 
@@ -16,27 +19,50 @@ class MultiSourceQueue {
 public:
     class Producer {
     public:
+        explicit Producer(MultiSourceQueue& owner) noexcept : owner_(owner) {}
+
+        ~Producer() { Publish(); }
+
         void Insert(const T& value) noexcept { queue_.push_back(value); }
 
+        // Merge `this` queue with owning `MultiSourceQueue`. `this` will have empty queue after the call.
+        // This call is performed without heap allocations. TODO: Test that no allocations are happening.
+        void Publish() noexcept { owner_.Collect(*this); }
+
     private:
         friend class MultiSourceQueue;
 
+        MultiSourceQueue& owner_; // weak
         std::list<T> queue_;
     };
 
     using Iterator = typename std::list<T>::iterator;
 
-    Iterator begin() noexcept { return commonQueue_.begin(); }
-    Iterator end() noexcept { return commonQueue_.end(); }
+    class Iterable : MoveOnly {
+    public:
+        explicit Iterable(MultiSourceQueue& owner) noexcept : owner_(owner), guard_(owner_.mutex_) {}
 
-    // Merge `producer`s queue with `this`. `producer` will have empty queue after the call.
-    // This call is performed without heap allocations. TODO: Test that no allocations are happening.
-    void Collect(Producer* producer) noexcept { commonQueue_.splice(commonQueue_.end(), producer->queue_); }
+        Iterator begin() noexcept { return owner_.commonQueue_.begin(); }
+        Iterator end() noexcept { return owner_.commonQueue_.end(); }
+
+    private:
+        MultiSourceQueue& owner_; // weak
+        std::unique_lock<SimpleMutex> guard_;
+    };
+
+    // Lock MultiSourceQueue for safe iteration.
+    Iterable Iter() noexcept { return Iterable(*this); }
 
 private:
+    void Collect(Producer& producer) noexcept {
+        std::lock_guard<SimpleMutex> guard(mutex_);
+        commonQueue_.splice(commonQueue_.end(), producer.queue_);
+    }
+
     // Using `std::list` as it allows to implement `Collect` without memory allocations,
     // which is important for GC mark phase.
     std::list<T> commonQueue_;
+    SimpleMutex mutex_;
 };
 
 } // namespace kotlin
diff --git a/kotlin-native/runtime/src/main/cpp/MultiSourceQueueTest.cpp b/kotlin-native/runtime/src/main/cpp/MultiSourceQueueTest.cpp
index e6622edc099..60d8e81fa66 100644
--- a/kotlin-native/runtime/src/main/cpp/MultiSourceQueueTest.cpp
+++ b/kotlin-native/runtime/src/main/cpp/MultiSourceQueueTest.cpp
@@ -5,9 +5,14 @@
 
 #include "MultiSourceQueue.hpp"
 
+#include <atomic>
+#include <thread>
+
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 
+#include "TestSupport.hpp"
+
 using namespace kotlin;
 
 using IntQueue = MultiSourceQueue<int>;
@@ -16,74 +21,187 @@ TEST(MultiSourceQueueTest, Empty) {
     IntQueue queue;
 
     std::vector<int> actual;
-    for (int element : queue) {
+    for (int element : queue.Iter()) {
         actual.push_back(element);
     }
 
     EXPECT_THAT(actual, testing::IsEmpty());
 }
 
-TEST(MultiSourceQueueTest, DoNotCollect) {
+TEST(MultiSourceQueueTest, DoNotPublish) {
     IntQueue queue;
-    IntQueue::Producer producer;
+    IntQueue::Producer producer(queue);
 
     producer.Insert(1);
     producer.Insert(2);
 
     std::vector<int> actual;
-    for (int element : queue) {
+    for (int element : queue.Iter()) {
         actual.push_back(element);
     }
 
     EXPECT_THAT(actual, testing::IsEmpty());
 }
 
-TEST(MultiSourceQueueTest, Collect) {
+TEST(MultiSourceQueueTest, Publish) {
     IntQueue queue;
-    IntQueue::Producer producer1;
-    IntQueue::Producer producer2;
+    IntQueue::Producer producer1(queue);
+    IntQueue::Producer producer2(queue);
 
     producer1.Insert(1);
     producer1.Insert(2);
     producer2.Insert(10);
     producer2.Insert(20);
 
-    queue.Collect(&producer1);
-    queue.Collect(&producer2);
+    producer1.Publish();
+    producer2.Publish();
 
     std::vector<int> actual;
-    for (int element : queue) {
+    for (int element : queue.Iter()) {
         actual.push_back(element);
     }
 
     EXPECT_THAT(actual, testing::ElementsAre(1, 2, 10, 20));
 }
 
-TEST(MultiSourceQueueTest, CollectSeveralTimes) {
+TEST(MultiSourceQueueTest, PublishSeveralTimes) {
     IntQueue queue;
-    IntQueue::Producer producer;
+    IntQueue::Producer producer(queue);
 
-    // Add 2 elements and collect.
+    // Add 2 elements and publish.
     producer.Insert(1);
     producer.Insert(2);
-    queue.Collect(&producer);
+    producer.Publish();
 
-    // Add another element and collect.
+    // Add another element and publish.
     producer.Insert(3);
-    queue.Collect(&producer);
+    producer.Publish();
 
-    // Collect without adding elements.
-    queue.Collect(&producer);
+    // Publish without adding elements.
+    producer.Publish();
 
-    // Add yet another two elements and collect.
+    // Add yet another two elements and publish.
     producer.Insert(4);
     producer.Insert(5);
-    queue.Collect(&producer);
+    producer.Publish();
 
     std::vector<int> actual;
-    for (int element : queue) {
+    for (int element : queue.Iter()) {
         actual.push_back(element);
     }
 
     EXPECT_THAT(actual, testing::ElementsAre(1, 2, 3, 4, 5));
 }
+
+TEST(MultiSourceQueueTest, PublishInDestructor) {
+    IntQueue queue;
+
+    {
+        IntQueue::Producer producer(queue);
+        producer.Insert(1);
+        producer.Insert(2);
+    }
+
+    std::vector<int> actual;
+    for (int element : queue.Iter()) {
+        actual.push_back(element);
+    }
+
+    EXPECT_THAT(actual, testing::ElementsAre(1, 2));
+}
+
+TEST(MultiSourceQueueTest, ConcurrentPublish) {
+    IntQueue queue;
+    constexpr int kThreadCount = kDefaultThreadCount;
+    std::atomic<bool> canStart(false);
+    std::atomic<int> readyCount(0);
+    std::vector<std::thread> threads;
+    std::vector<int> expected;
+
+    for (int i = 0; i < kThreadCount; ++i) {
+        expected.push_back(i);
+        threads.emplace_back([i, &queue, &canStart, &readyCount]() {
+            IntQueue::Producer producer(queue);
+            producer.Insert(i);
+            ++readyCount;
+            while (!canStart) {
+            }
+            producer.Publish();
+        });
+    }
+
+    while (readyCount < kThreadCount) {
+    }
+    canStart = true;
+    for (auto& t : threads) {
+        t.join();
+    }
+
+    std::vector<int> actual;
+    for (int element : queue.Iter()) {
+        actual.push_back(element);
+    }
+
+    EXPECT_THAT(actual, testing::UnorderedElementsAreArray(expected));
+}
+
+TEST(MultiSourceQueueTest, IterWhileConcurrentPublish) {
+    IntQueue queue;
+    constexpr int kStartCount = 50;
+    constexpr int kThreadCount = kDefaultThreadCount;
+
+    std::vector<int> expectedBefore;
+    std::vector<int> expectedAfter;
+    IntQueue::Producer producer(queue);
+    for (int i = 0; i < kStartCount; ++i) {
+        expectedBefore.push_back(i);
+        expectedAfter.push_back(i);
+        producer.Insert(i);
+    }
+    producer.Publish();
+
+    std::atomic<bool> canStart(false);
+    std::atomic<int> readyCount(0);
+    std::atomic<int> startedCount(0);
+    std::vector<std::thread> threads;
+    for (int i = 0; i < kThreadCount; ++i) {
+        int j = i + kStartCount;
+        expectedAfter.push_back(j);
+        threads.emplace_back([j, &queue, &canStart, &startedCount, &readyCount]() {
+            IntQueue::Producer producer(queue);
+            producer.Insert(j);
+            ++readyCount;
+            while (!canStart) {
+            }
+            ++startedCount;
+            producer.Publish();
+        });
+    }
+
+    std::vector<int> actualBefore;
+    {
+        auto iter = queue.Iter();
+        while (readyCount < kThreadCount) {
+        }
+        canStart = true;
+        while (startedCount < kThreadCount) {
+        }
+
+        for (int element : iter) {
+            actualBefore.push_back(element);
+        }
+    }
+
+    for (auto& t : threads) {
+        t.join();
+    }
+
+    EXPECT_THAT(actualBefore, testing::ElementsAreArray(expectedBefore));
+
+    std::vector<int> actualAfter;
+    for (int element : queue.Iter()) {
+        actualAfter.push_back(element);
+    }
+
+    EXPECT_THAT(actualAfter, testing::UnorderedElementsAreArray(expectedAfter));
+}
diff --git a/kotlin-native/runtime/src/main/cpp/SingleLockListTest.cpp b/kotlin-native/runtime/src/main/cpp/SingleLockListTest.cpp
index 2fd1d93b338..480056ac12f 100644
--- a/kotlin-native/runtime/src/main/cpp/SingleLockListTest.cpp
+++ b/kotlin-native/runtime/src/main/cpp/SingleLockListTest.cpp
@@ -12,6 +12,8 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 
+#include "TestSupport.hpp"
+
 using namespace kotlin;
 
 namespace {
@@ -105,19 +107,23 @@ TEST(SingleLockListTest, EraseToEmptyEmplaceAndIter) {
 
 TEST(SingleLockListTest, ConcurrentEmplace) {
     IntList list;
-    constexpr int kThreadCount = 100;
+    constexpr int kThreadCount = kDefaultThreadCount;
     std::atomic<bool> canStart(false);
+    std::atomic<int> readyCount(0);
     std::vector<std::thread> threads;
     std::vector<int> expected;
     for (int i = 0; i < kThreadCount; ++i) {
         expected.push_back(i);
-        threads.emplace_back([i, &list, &canStart]() {
+        threads.emplace_back([i, &list, &canStart, &readyCount]() {
+            ++readyCount;
             while (!canStart) {
             }
             list.Emplace(i);
         });
     }
 
+    while (readyCount < kThreadCount) {
+    }
     canStart = true;
     for (auto& t : threads) {
         t.join();
@@ -133,22 +139,26 @@ TEST(SingleLockListTest, ConcurrentEmplace) {
 
 TEST(SingleLockListTest, ConcurrentErase) {
     IntList list;
-    constexpr int kThreadCount = 100;
+    constexpr int kThreadCount = kDefaultThreadCount;
     std::vector<IntList::Node*> items;
     for (int i = 0; i < kThreadCount; ++i) {
         items.push_back(list.Emplace(i));
     }
 
     std::atomic<bool> canStart(false);
+    std::atomic<int> readyCount(0);
     std::vector<std::thread> threads;
     for (auto* item : items) {
-        threads.emplace_back([item, &list, &canStart]() {
+        threads.emplace_back([item, &list, &canStart, &readyCount]() {
+            ++readyCount;
             while (!canStart) {
             }
             list.Erase(item);
         });
     }
 
+    while (readyCount < kThreadCount) {
+    }
     canStart = true;
     for (auto& t : threads) {
         t.join();
@@ -165,7 +175,7 @@ TEST(SingleLockListTest, ConcurrentErase) {
 TEST(SingleLockListTest, IterWhileConcurrentEmplace) {
     IntList list;
     constexpr int kStartCount = 50;
-    constexpr int kThreadCount = 100;
+    constexpr int kThreadCount = kDefaultThreadCount;
 
     std::deque<int> expectedBefore;
     std::vector<int> expectedAfter;
@@ -217,7 +227,7 @@ TEST(SingleLockListTest, IterWhileConcurrentEmplace) {
 
 TEST(SingleLockListTest, IterWhileConcurrentErase) {
     IntList list;
-    constexpr int kThreadCount = 100;
+    constexpr int kThreadCount = kDefaultThreadCount;
 
     std::deque<int> expectedBefore;
     std::vector<IntList::Node*> items;
diff --git a/kotlin-native/runtime/src/main/cpp/TestSupport.hpp b/kotlin-native/runtime/src/main/cpp/TestSupport.hpp
new file mode 100644
index 00000000000..521a7d93951
--- /dev/null
+++ b/kotlin-native/runtime/src/main/cpp/TestSupport.hpp
@@ -0,0 +1,15 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+
+namespace kotlin {
+
+#if KONAN_WINDOWS
+// TODO: Figure out why creating many threads on windows is so slow.
+constexpr int kDefaultThreadCount = 10;
+#else
+constexpr int kDefaultThreadCount = 100;
+#endif
+
+} // namespace kotlin
diff --git a/kotlin-native/runtime/src/mm/cpp/GlobalsRegistry.cpp b/kotlin-native/runtime/src/mm/cpp/GlobalsRegistry.cpp
index 96f80fd9ea4..74c89ea7747 100644
--- a/kotlin-native/runtime/src/mm/cpp/GlobalsRegistry.cpp
+++ b/kotlin-native/runtime/src/mm/cpp/GlobalsRegistry.cpp
@@ -18,12 +18,11 @@ mm::GlobalsRegistry& mm::GlobalsRegistry::Instance() noexcept {
 }
 
 void mm::GlobalsRegistry::RegisterStorageForGlobal(mm::ThreadData* threadData, ObjHeader** location) noexcept {
-    threadData->globalsThreadQueue()->Insert(location);
+    threadData->globalsThreadQueue().Insert(location);
 }
 
 void mm::GlobalsRegistry::ProcessThread(mm::ThreadData* threadData) noexcept {
-    RuntimeAssert(threadData->isWaitingForGC(), "Thread must be waiting for GC to complete.");
-    globals_.Collect(threadData->globalsThreadQueue());
+    threadData->globalsThreadQueue().Publish();
 }
 
 mm::GlobalsRegistry::GlobalsRegistry() = default;
diff --git a/kotlin-native/runtime/src/mm/cpp/GlobalsRegistry.hpp b/kotlin-native/runtime/src/mm/cpp/GlobalsRegistry.hpp
index 5cb77c91128..580ddf74ce4 100644
--- a/kotlin-native/runtime/src/mm/cpp/GlobalsRegistry.hpp
+++ b/kotlin-native/runtime/src/mm/cpp/GlobalsRegistry.hpp
@@ -16,24 +16,29 @@ namespace mm {
 
 class GlobalsRegistry : Pinned {
 public:
-    using ThreadQueue = MultiSourceQueue<ObjHeader**>::Producer;
+    class ThreadQueue : public MultiSourceQueue<ObjHeader**>::Producer {
+    public:
+        explicit ThreadQueue(GlobalsRegistry& registry) : Producer(registry.globals_) {}
+        // Do not add fields as this is just a wrapper and Producer does not have virtual destructor.
+    };
 
-    using Iterator = std::list<ObjHeader**>::iterator;
+    using Iterable = MultiSourceQueue<ObjHeader**>::Iterable;
+
+    using Iterator = MultiSourceQueue<ObjHeader**>::Iterator;
 
     static GlobalsRegistry& Instance() noexcept;
 
     void RegisterStorageForGlobal(mm::ThreadData* threadData, ObjHeader** location) noexcept;
 
-    // Collect globals from thread corresponding to `threadData`. Thread must be waiting for GC.
-    // Only one thread can call this method.
+    // Collect globals from thread corresponding to `threadData`. Must be called by the thread
+    // when it's asked by GC to stop.
     void ProcessThread(mm::ThreadData* threadData) noexcept;
 
-    // These must be called on the same thread as `ProcessThread` to avoid races.
+    // Lock registry for safe iteration.
     // TODO: Iteration over `globals_` will be slow, because it's `std::list` 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.
-    Iterator begin() noexcept { return globals_.begin(); }
-    Iterator end() noexcept { return globals_.end(); }
+    Iterable Iter() noexcept { return globals_.Iter(); }
 
 private:
     friend class GlobalData;
diff --git a/kotlin-native/runtime/src/mm/cpp/ThreadData.hpp b/kotlin-native/runtime/src/mm/cpp/ThreadData.hpp
index 82a89c3c3f2..cecf7cdb2d6 100644
--- a/kotlin-native/runtime/src/mm/cpp/ThreadData.hpp
+++ b/kotlin-native/runtime/src/mm/cpp/ThreadData.hpp
@@ -19,18 +19,13 @@ namespace mm {
 // Pin it in memory to prevent accidental copying.
 class ThreadData final : private Pinned {
 public:
-    ThreadData(pthread_t threadId) noexcept : threadId_(threadId) {}
+    ThreadData(pthread_t threadId) noexcept : threadId_(threadId), globalsThreadQueue_(GlobalsRegistry::Instance()) {}
 
     ~ThreadData() = default;
 
     pthread_t threadId() const noexcept { return threadId_; }
 
-    bool isWaitingForGC() const noexcept {
-        // TODO: Implement.
-        return false;
-    }
-
-    GlobalsRegistry::ThreadQueue* globalsThreadQueue() noexcept { return &globalsThreadQueue_; }
+    GlobalsRegistry::ThreadQueue& globalsThreadQueue() noexcept { return globalsThreadQueue_; }
 
     ThreadLocalStorage& tls() noexcept { return tls_; }