Remove the future serial

This adds 'HasScheduledCommands()', with which Dawn no longer needs the
future serial to tick and track the async tasks.

Bug: dawn:1413
Change-Id: Ide9ba69b796a46fa8bb70b002f4e2aeb1622bffd
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/98720
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Jie A Chen <jie.a.chen@intel.com>

src/dawn/native/Buffer.cpp

@@ -21,6 +21,7 @@
 
 #include "dawn/common/Alloc.h"
 #include "dawn/common/Assert.h"
+#include "dawn/native/CallbackTaskManager.h"
 #include "dawn/native/Commands.h"
 #include "dawn/native/Device.h"
 #include "dawn/native/DynamicUploader.h"
@@ -34,16 +35,21 @@
 namespace dawn::native {
 
 namespace {
-struct MapRequestTask : QueueBase::TaskInFlight {
+struct MapRequestTask : TrackTaskCallback {
-    MapRequestTask(Ref<BufferBase> buffer, MapRequestID id) : buffer(std::move(buffer)), id(id) {}
+    MapRequestTask(dawn::platform::Platform* platform, Ref<BufferBase> buffer, MapRequestID id)
-    void Finish(dawn::platform::Platform* platform, ExecutionSerial serial) override {
+        : TrackTaskCallback(platform), buffer(std::move(buffer)), id(id) {}
-        TRACE_EVENT1(platform, General, "Buffer::TaskInFlight::Finished", "serial",
+    void Finish() override {
-                     uint64_t(serial));
+        ASSERT(mSerial != kMaxExecutionSerial);
+        TRACE_EVENT1(mPlatform, General, "Buffer::TaskInFlight::Finished", "serial",
+                     uint64_t(mSerial));
         buffer->OnMapRequestCompleted(id, WGPUBufferMapAsyncStatus_Success);
     }
     void HandleDeviceLoss() override {
         buffer->OnMapRequestCompleted(id, WGPUBufferMapAsyncStatus_DeviceLost);
     }
+    void HandleShutDown() override {
+        buffer->OnMapRequestCompleted(id, WGPUBufferMapAsyncStatus_DestroyedBeforeCallback);
+    }
     ~MapRequestTask() override = default;
 
   private:
@@ -353,10 +359,11 @@ void BufferBase::APIMapAsync(wgpu::MapMode mode,
         CallMapCallback(mLastMapID, WGPUBufferMapAsyncStatus_DeviceLost);
         return;
     }
-    std::unique_ptr<MapRequestTask> request = std::make_unique<MapRequestTask>(this, mLastMapID);
+    std::unique_ptr<MapRequestTask> request =
+        std::make_unique<MapRequestTask>(GetDevice()->GetPlatform(), this, mLastMapID);
     TRACE_EVENT1(GetDevice()->GetPlatform(), General, "Buffer::APIMapAsync", "serial",
                  uint64_t(GetDevice()->GetPendingCommandSerial()));
-    GetDevice()->GetQueue()->TrackTask(std::move(request), GetDevice()->GetPendingCommandSerial());
+    GetDevice()->GetQueue()->TrackTask(std::move(request));
 }
 
 void* BufferBase::APIGetMappedRange(size_t offset, size_t size) {

src/dawn/native/Device.cpp

@@ -428,7 +428,6 @@ void DeviceBase::Destroy() {
             break;
     }
     ASSERT(mCompletedSerial == mLastSubmittedSerial);
-    ASSERT(mFutureSerial <= mCompletedSerial);
 
     if (mState != State::BeingCreated) {
         // The GPU timeline is finished.
@@ -440,6 +439,9 @@ void DeviceBase::Destroy() {
         // Call TickImpl once last time to clean up resources
         // Ignore errors so that we can continue with destruction
         IgnoreErrors(TickImpl());
+
+        // Trigger all in-flight TrackTask callbacks from 'mQueue'.
+        FlushCallbackTaskQueue();
     }
 
     // At this point GPU operations are always finished, so we are in the disconnected state.
@@ -499,7 +501,6 @@ void DeviceBase::HandleError(InternalErrorType type,
         IgnoreErrors(WaitForIdleForDestruction());
         IgnoreErrors(TickImpl());
         AssumeCommandsComplete();
-        ASSERT(mFutureSerial <= mCompletedSerial);
         mState = State::Disconnected;
 
         // Now everything is as if the device was lost.
@@ -694,10 +695,6 @@ ExecutionSerial DeviceBase::GetLastSubmittedCommandSerial() const {
     return mLastSubmittedSerial;
 }
 
-ExecutionSerial DeviceBase::GetFutureSerial() const {
-    return mFutureSerial;
-}
-
 InternalPipelineStore* DeviceBase::GetInternalPipelineStore() {
     return mInternalPipelineStore.get();
 }
@@ -707,10 +704,9 @@ void DeviceBase::IncrementLastSubmittedCommandSerial() {
 }
 
 void DeviceBase::AssumeCommandsComplete() {
-    ExecutionSerial maxSerial =
+    // Bump serials so any pending callbacks can be fired.
-        ExecutionSerial(std::max(mLastSubmittedSerial + ExecutionSerial(1), mFutureSerial));
+    mLastSubmittedSerial++;
-    mLastSubmittedSerial = maxSerial;
+    mCompletedSerial = mLastSubmittedSerial;
-    mCompletedSerial = maxSerial;
 }
 
 bool DeviceBase::IsDeviceIdle() {
@@ -720,24 +716,13 @@ bool DeviceBase::IsDeviceIdle() {
     if (!mCallbackTaskManager->IsEmpty()) {
         return false;
     }
-
+    return !HasScheduledCommands();
-    ExecutionSerial maxSerial = std::max(mLastSubmittedSerial, mFutureSerial);
-    if (mCompletedSerial == maxSerial) {
-        return true;
-    }
-    return false;
 }
 
 ExecutionSerial DeviceBase::GetPendingCommandSerial() const {
     return mLastSubmittedSerial + ExecutionSerial(1);
 }
 
-void DeviceBase::AddFutureSerial(ExecutionSerial serial) {
-    if (serial > mFutureSerial) {
-        mFutureSerial = serial;
-    }
-}
-
 MaybeError DeviceBase::CheckPassedSerials() {
     ExecutionSerial completedSerial;
     DAWN_TRY_ASSIGN(completedSerial, CheckAndUpdateCompletedSerials());
@@ -1241,21 +1226,13 @@ bool DeviceBase::APITick() {
 MaybeError DeviceBase::Tick() {
     DAWN_TRY(ValidateIsAlive());
 
-    // to avoid overly ticking, we only want to tick when:
+    // To avoid overly ticking, we only want to tick when:
     // 1. the last submitted serial has moved beyond the completed serial
-    // 2. or the completed serial has not reached the future serial set by the trackers
+    // 2. or the backend still has pending commands to submit.
-    if (mLastSubmittedSerial > mCompletedSerial || mCompletedSerial < mFutureSerial) {
+    if (HasScheduledCommands()) {
         DAWN_TRY(CheckPassedSerials());
         DAWN_TRY(TickImpl());
 
-        // There is no GPU work in flight, we need to move the serials forward so that
-        // so that CPU operations waiting on GPU completion can know they don't have to wait.
-        // AssumeCommandsComplete will assign the max serial we must tick to in order to
-        // fire the awaiting callbacks.
-        if (mCompletedSerial == mLastSubmittedSerial) {
-            AssumeCommandsComplete();
-        }
-
         // TODO(crbug.com/dawn/833): decouple TickImpl from updating the serial so that we can
         // tick the dynamic uploader before the backend resource allocators. This would allow
         // reclaiming resources one tick earlier.
@@ -1917,4 +1894,28 @@ uint64_t DeviceBase::GetBufferCopyOffsetAlignmentForDepthStencil() const {
     return 4u;
 }
 
+bool DeviceBase::HasScheduledCommands() const {
+    return mLastSubmittedSerial > mCompletedSerial || HasPendingCommands();
+}
+
+void DeviceBase::AssumeCommandsCompleteForTesting() {
+    AssumeCommandsComplete();
+}
+
+// All prevously submitted works at the moment will supposedly complete at this serial.
+// Internally the serial is computed according to whether frontend and backend have pending
+// commands. There are 4 cases of combination:
+//   1) Frontend(No), Backend(No)
+//   2) Frontend(No), Backend(Yes)
+//   3) Frontend(Yes), Backend(No)
+//   4) Frontend(Yes), Backend(Yes)
+// For case 1, we don't need the serial to track the task as we can ack it right now.
+// For case 2 and 4, there will be at least an eventual submission, so we can use
+// 'GetPendingCommandSerial' as the serial.
+// For case 3, we can't use 'GetPendingCommandSerial' as it won't be submitted surely. Instead we
+// use 'GetLastSubmittedCommandSerial', which must be fired eventually.
+ExecutionSerial DeviceBase::GetScheduledWorkDoneSerial() const {
+    return HasPendingCommands() ? GetPendingCommandSerial() : GetLastSubmittedCommandSerial();
+}
+
 }  // namespace dawn::native

src/dawn/native/Device.h

@@ -159,7 +159,6 @@ class DeviceBase : public RefCountedWithExternalCount {
 
     ExecutionSerial GetCompletedCommandSerial() const;
     ExecutionSerial GetLastSubmittedCommandSerial() const;
-    ExecutionSerial GetFutureSerial() const;
     ExecutionSerial GetPendingCommandSerial() const;
 
     // Many Dawn objects are completely immutable once created which means that if two
@@ -349,14 +348,6 @@ class DeviceBase : public RefCountedWithExternalCount {
     void APIForceLoss(wgpu::DeviceLostReason reason, const char* message);
     QueueBase* GetQueue() const;
 
-    // AddFutureSerial is used to update the mFutureSerial with the max serial needed to be
-    // ticked in order to clean up all pending callback work or to execute asynchronous resource
-    // writes. It should be given the serial that a callback is tracked with, so that once that
-    // serial is completed, it can be resolved and cleaned up. This is so that when there is no
-    // gpu work (the last submitted serial has not moved beyond the completed serial), Tick can
-    // still check if we have pending work to take care of, rather than hanging and never
-    // reaching the serial the work will be executed on.
-    void AddFutureSerial(ExecutionSerial serial);
     // Check for passed fences and set the new completed serial
     MaybeError CheckPassedSerials();
 
@@ -404,6 +395,16 @@ class DeviceBase : public RefCountedWithExternalCount {
 
     virtual void AppendDebugLayerMessages(ErrorData* error) {}
 
+    void AssumeCommandsCompleteForTesting();
+
+    // Whether the device is having scheduled commands to be submitted or executed.
+    // There are "Scheduled" "Pending" and "Executing" commands. Frontend knows "Executing" commands
+    // and backend knows "Pending" commands. "Scheduled" commands are either "Pending" or
+    // "Executing".
+    bool HasScheduledCommands() const;
+    // The serial by which time all currently submitted or pending operations will be completed.
+    ExecutionSerial GetScheduledWorkDoneSerial() const;
+
   protected:
     // Constructor used only for mocking and testing.
     DeviceBase();
@@ -497,14 +498,9 @@ class DeviceBase : public RefCountedWithExternalCount {
     // mCompletedSerial tracks the last completed command serial that the fence has returned.
     // mLastSubmittedSerial tracks the last submitted command serial.
     // During device removal, the serials could be artificially incremented
-    // to make it appear as if commands have been compeleted. They can also be artificially
+    // to make it appear as if commands have been compeleted.
-    // incremented when no work is being done in the GPU so CPU operations don't have to wait on
-    // stale serials.
-    // mFutureSerial tracks the largest serial we need to tick to for asynchronous commands or
-    // callbacks to fire
     ExecutionSerial mCompletedSerial = ExecutionSerial(0);
     ExecutionSerial mLastSubmittedSerial = ExecutionSerial(0);
-    ExecutionSerial mFutureSerial = ExecutionSerial(0);
 
     // DestroyImpl is used to clean up and release resources used by device, does not wait for
     // GPU or check errors.
@@ -516,6 +512,9 @@ class DeviceBase : public RefCountedWithExternalCount {
     // resources.
     virtual MaybeError WaitForIdleForDestruction() = 0;
 
+    // Indicates whether the backend has pending commands to be submitted as soon as possible.
+    virtual bool HasPendingCommands() const = 0;
+
     wgpu::ErrorCallback mUncapturedErrorCallback = nullptr;
     void* mUncapturedErrorUserdata = nullptr;
 

src/dawn/native/Queue.cpp

@@ -130,13 +130,16 @@ ResultOrError<UploadHandle> UploadTextureDataAligningBytesPerRowAndOffset(
     return uploadHandle;
 }
 
-struct SubmittedWorkDone : QueueBase::TaskInFlight {
+struct SubmittedWorkDone : TrackTaskCallback {
-    SubmittedWorkDone(WGPUQueueWorkDoneCallback callback, void* userdata)
+    SubmittedWorkDone(dawn::platform::Platform* platform,
-        : mCallback(callback), mUserdata(userdata) {}
+                      WGPUQueueWorkDoneCallback callback,
-    void Finish(dawn::platform::Platform* platform, ExecutionSerial serial) override {
+                      void* userdata)
+        : TrackTaskCallback(platform), mCallback(callback), mUserdata(userdata) {}
+    void Finish() override {
         ASSERT(mCallback != nullptr);
-        TRACE_EVENT1(platform, General, "Queue::SubmittedWorkDone::Finished", "serial",
+        ASSERT(mSerial != kMaxExecutionSerial);
-                     uint64_t(serial));
+        TRACE_EVENT1(mPlatform, General, "Queue::SubmittedWorkDone::Finished", "serial",
+                     uint64_t(mSerial));
         mCallback(WGPUQueueWorkDoneStatus_Success, mUserdata);
         mCallback = nullptr;
     }
@@ -145,6 +148,7 @@ struct SubmittedWorkDone : QueueBase::TaskInFlight {
         mCallback(WGPUQueueWorkDoneStatus_DeviceLost, mUserdata);
         mCallback = nullptr;
     }
+    void HandleShutDown() override { HandleDeviceLoss(); }
     ~SubmittedWorkDone() override = default;
 
   private:
@@ -163,9 +167,11 @@ class ErrorQueue : public QueueBase {
 };
 }  // namespace
 
-// QueueBase
+void TrackTaskCallback::SetFinishedSerial(ExecutionSerial serial) {
+    mSerial = serial;
+}
 
-QueueBase::TaskInFlight::~TaskInFlight() {}
+// QueueBase
 
 QueueBase::QueueBase(DeviceBase* device, const QueueDescriptor* descriptor)
     : ApiObjectBase(device, descriptor->label) {}
@@ -206,21 +212,27 @@ void QueueBase::APIOnSubmittedWorkDone(uint64_t signalValue,
     }
 
     std::unique_ptr<SubmittedWorkDone> task =
-        std::make_unique<SubmittedWorkDone>(callback, userdata);
+        std::make_unique<SubmittedWorkDone>(GetDevice()->GetPlatform(), callback, userdata);
 
     // Technically we only need to wait for previously submitted work but OnSubmittedWorkDone is
     // also used to make sure ALL queue work is finished in tests, so we also wait for pending
     // commands (this is non-observable outside of tests so it's ok to do deviate a bit from the
     // spec).
-    TrackTask(std::move(task), GetDevice()->GetPendingCommandSerial());
+    TrackTask(std::move(task));
 
     TRACE_EVENT1(GetDevice()->GetPlatform(), General, "Queue::APIOnSubmittedWorkDone", "serial",
                  uint64_t(GetDevice()->GetPendingCommandSerial()));
 }
 
-void QueueBase::TrackTask(std::unique_ptr<TaskInFlight> task, ExecutionSerial serial) {
+void QueueBase::TrackTask(std::unique_ptr<TrackTaskCallback> task) {
-    mTasksInFlight.Enqueue(std::move(task), serial);
+    // we can move the task to the callback task manager, as it's ready to be called if there are no
-    GetDevice()->AddFutureSerial(serial);
+    // scheduled commands.
+    if (!GetDevice()->HasScheduledCommands()) {
+        task->SetFinishedSerial(GetDevice()->GetCompletedCommandSerial());
+        GetDevice()->GetCallbackTaskManager()->AddCallbackTask(std::move(task));
+    } else {
+        mTasksInFlight.Enqueue(std::move(task), GetDevice()->GetScheduledWorkDoneSerial());
+    }
 }
 
 void QueueBase::Tick(ExecutionSerial finishedSerial) {
@@ -232,14 +244,17 @@ void QueueBase::Tick(ExecutionSerial finishedSerial) {
     TRACE_EVENT1(GetDevice()->GetPlatform(), General, "Queue::Tick", "finishedSerial",
                  uint64_t(finishedSerial));
 
-    std::vector<std::unique_ptr<TaskInFlight>> tasks;
+    std::vector<std::unique_ptr<TrackTaskCallback>> tasks;
     for (auto& task : mTasksInFlight.IterateUpTo(finishedSerial)) {
         tasks.push_back(std::move(task));
     }
     mTasksInFlight.ClearUpTo(finishedSerial);
 
+    // Tasks' serials have passed. Move them to the callback task manager. They
+    // are ready to be called.
     for (auto& task : tasks) {
-        task->Finish(GetDevice()->GetPlatform(), finishedSerial);
+        task->SetFinishedSerial(finishedSerial);
+        GetDevice()->GetCallbackTaskManager()->AddCallbackTask(std::move(task));
     }
 }
 
@@ -286,8 +301,6 @@ MaybeError QueueBase::WriteBufferImpl(BufferBase* buffer,
 
     memcpy(uploadHandle.mappedBuffer, data, size);
 
-    device->AddFutureSerial(device->GetPendingCommandSerial());
-
     return device->CopyFromStagingToBuffer(uploadHandle.stagingBuffer, uploadHandle.startOffset,
                                            buffer, bufferOffset, size);
 }
@@ -356,8 +369,6 @@ MaybeError QueueBase::WriteTextureImpl(const ImageCopyTexture& destination,
 
     DeviceBase* device = GetDevice();
 
-    device->AddFutureSerial(device->GetPendingCommandSerial());
-
     return device->CopyFromStagingToTexture(uploadHandle.stagingBuffer, passDataLayout,
                                             &textureCopy, writeSizePixel);
 }

src/dawn/native/Queue.h

@@ -18,6 +18,7 @@
 #include <memory>
 
 #include "dawn/common/SerialQueue.h"
+#include "dawn/native/CallbackTaskManager.h"
 #include "dawn/native/Error.h"
 #include "dawn/native/Forward.h"
 #include "dawn/native/IntegerTypes.h"
@@ -29,14 +30,23 @@
 
 namespace dawn::native {
 
+// For the commands with async callback like 'MapAsync' and 'OnSubmittedWorkDone', we track the
+// execution serials of completion in the queue for them. This implements 'CallbackTask' so that the
+// aysnc callback can be fired by 'CallbackTaskManager' in a unified way. This also caches the
+// finished serial, as the callback needs to use it in the trace event.
+struct TrackTaskCallback : CallbackTask {
+    explicit TrackTaskCallback(dawn::platform::Platform* platform) : mPlatform(platform) {}
+    void SetFinishedSerial(ExecutionSerial serial);
+    ~TrackTaskCallback() override = default;
+
+  protected:
+    dawn::platform::Platform* mPlatform = nullptr;
+    // The serial by which time the callback can be fired.
+    ExecutionSerial mSerial = kMaxExecutionSerial;
+};
+
 class QueueBase : public ApiObjectBase {
   public:
-    struct TaskInFlight {
-        virtual ~TaskInFlight();
-        virtual void Finish(dawn::platform::Platform* platform, ExecutionSerial serial) = 0;
-        virtual void HandleDeviceLoss() = 0;
-    };
-
     ~QueueBase() override;
 
     static QueueBase* MakeError(DeviceBase* device);
@@ -67,7 +77,7 @@ class QueueBase : public ApiObjectBase {
                            uint64_t bufferOffset,
                            const void* data,
                            size_t size);
-    void TrackTask(std::unique_ptr<TaskInFlight> task, ExecutionSerial serial);
+    void TrackTask(std::unique_ptr<TrackTaskCallback> task);
     void Tick(ExecutionSerial finishedSerial);
     void HandleDeviceLoss();
 
@@ -111,7 +121,7 @@ class QueueBase : public ApiObjectBase {
 
     void SubmitInternal(uint32_t commandCount, CommandBufferBase* const* commands);
 
-    SerialQueue<ExecutionSerial, std::unique_ptr<TaskInFlight>> mTasksInFlight;
+    SerialQueue<ExecutionSerial, std::unique_ptr<TrackTaskCallback>> mTasksInFlight;
 };
 
 }  // namespace dawn::native

src/dawn/native/d3d12/DeviceD3D12.cpp

@@ -400,6 +400,10 @@ void Device::ReferenceUntilUnused(ComPtr<IUnknown> object) {
     mUsedComObjectRefs.Enqueue(object, GetPendingCommandSerial());
 }
 
+bool Device::HasPendingCommands() const {
+    return mPendingCommands.IsOpen();
+}
+
 MaybeError Device::ExecutePendingCommandContext() {
     return mPendingCommands.ExecuteCommandList(this);
 }

src/dawn/native/d3d12/DeviceD3D12.h

@@ -208,6 +208,7 @@ class Device final : public DeviceBase {
 
     void DestroyImpl() override;
     MaybeError WaitForIdleForDestruction() override;
+    bool HasPendingCommands() const override;
 
     MaybeError CheckDebugLayerAndGenerateErrors();
     void AppendDebugLayerMessages(ErrorData* error) override;

src/dawn/native/metal/DeviceMTL.h

@@ -127,6 +127,7 @@ class Device final : public DeviceBase {
     void InitTogglesFromDriver();
     void DestroyImpl() override;
     MaybeError WaitForIdleForDestruction() override;
+    bool HasPendingCommands() const override;
     ResultOrError<ExecutionSerial> CheckAndUpdateCompletedSerials() override;
 
     NSPRef<id<MTLDevice>> mMtlDevice;

src/dawn/native/metal/DeviceMTL.mm

@@ -369,6 +369,10 @@ CommandRecordingContext* Device::GetPendingCommandContext() {
     return &mCommandContext;
 }
 
+bool Device::HasPendingCommands() const {
+    return mCommandContext.WasUsed();
+}
+
 MaybeError Device::SubmitPendingCommandBuffer() {
     if (!mCommandContext.WasUsed()) {
         return {};

src/dawn/native/null/DeviceNull.cpp

@@ -213,6 +213,10 @@ MaybeError Device::WaitForIdleForDestruction() {
     return {};
 }
 
+bool Device::HasPendingCommands() const {
+    return false;
+}
+
 MaybeError Device::CopyFromStagingToBuffer(StagingBufferBase* source,
                                            uint64_t sourceOffset,
                                            BufferBase* destination,

src/dawn/native/null/DeviceNull.h

@@ -161,6 +161,7 @@ class Device final : public DeviceBase {
 
     void DestroyImpl() override;
     MaybeError WaitForIdleForDestruction() override;
+    bool HasPendingCommands() const override;
 
     std::vector<std::unique_ptr<PendingOperation>> mPendingOperations;
 

src/dawn/native/opengl/DeviceGL.cpp

@@ -446,6 +446,12 @@ MaybeError Device::WaitForIdleForDestruction() {
     return {};
 }
 
+bool Device::HasPendingCommands() const {
+    // Technically we could have scheduled commands inside the GL driver that are waiting for a
+    // glFlush but we can't know for sure so we might as well pretend there are no commands.
+    return false;
+}
+
 uint32_t Device::GetOptimalBytesPerRowAlignment() const {
     return 1;
 }

src/dawn/native/opengl/DeviceGL.h

@@ -132,6 +132,7 @@ class Device final : public DeviceBase {
     ResultOrError<ExecutionSerial> CheckAndUpdateCompletedSerials() override;
     void DestroyImpl() override;
     MaybeError WaitForIdleForDestruction() override;
+    bool HasPendingCommands() const override;
 
     const OpenGLFunctions mGL;
 

src/dawn/native/vulkan/DeviceVk.cpp

@@ -288,6 +288,10 @@ CommandRecordingContext* Device::GetPendingRecordingContext() {
     return &mRecordingContext;
 }
 
+bool Device::HasPendingCommands() const {
+    return mRecordingContext.used;
+}
+
 MaybeError Device::SubmitPendingCommands() {
     if (!mRecordingContext.used) {
         return {};

src/dawn/native/vulkan/DeviceVk.h

@@ -171,6 +171,7 @@ class Device final : public DeviceBase {
 
     void DestroyImpl() override;
     MaybeError WaitForIdleForDestruction() override;
+    bool HasPendingCommands() const override;
 
     // To make it easier to use fn it is a public const member. However
     // the Device is allowed to mutate them through these private methods.

src/dawn/tests/unittests/native/mocks/DeviceMock.h

@@ -116,6 +116,7 @@ class DeviceMock : public DeviceBase {
     MOCK_METHOD(ResultOrError<ExecutionSerial>, CheckAndUpdateCompletedSerials, (), (override));
     MOCK_METHOD(void, DestroyImpl, (), (override));
     MOCK_METHOD(MaybeError, WaitForIdleForDestruction, (), (override));
+    MOCK_METHOD(bool, HasPendingCommands, (), (const, override));
 };
 
 }  // namespace dawn::native

src/dawn/tests/white_box/D3D12DescriptorHeapTests.cpp

@@ -322,11 +322,8 @@ TEST_P(D3D12DescriptorHeapTests, PoolHeapsInPendingAndMultipleSubmits) {
               heapSerial + HeapVersionID(kNumOfSwitches));
     EXPECT_EQ(allocator->GetShaderVisiblePoolSizeForTesting(), kNumOfSwitches);
 
-    // Ensure switched-over heaps can be recycled by advancing the GPU by at-least
+    // Ensure switched-over heaps can be recycled by advancing the GPU.
-    // |kFrameDepth|.
+    mD3DDevice->AssumeCommandsCompleteForTesting();
-    for (uint32_t i = 0; i < kFrameDepth; i++) {
-        mD3DDevice->APITick();
-    }
 
     // Switch-over |kNumOfSwitches| again reusing the same heaps.
     for (uint32_t i = 0; i < kNumOfSwitches; i++) {
@@ -414,11 +411,8 @@ TEST_P(D3D12DescriptorHeapTests, GrowAndPoolHeapsInPendingAndMultipleSubmits) {
 
     EXPECT_EQ(allocator->GetShaderVisiblePoolSizeForTesting(), kNumOfPooledHeaps);
 
-    // Ensure switched-over heaps can be recycled by advancing the GPU by at-least
+    // Ensure switched-over heaps can be recycled by advancing the GPU.
-    // |kFrameDepth|.
+    mD3DDevice->AssumeCommandsCompleteForTesting();
-    for (uint32_t i = 0; i < kFrameDepth; i++) {
-        mD3DDevice->APITick();
-    }
 
     // Switch-over the pool-allocated heaps.
     for (uint32_t i = 0; i < kNumOfPooledHeaps; i++) {

src/dawn/tests/white_box/D3D12ResidencyTests.cpp

@@ -202,6 +202,12 @@ TEST_P(D3D12ResourceResidencyTests, AsyncMappedBufferRead) {
     // The mappable buffer should be resident.
     EXPECT_TRUE(CheckIfBufferIsResident(buffer));
 
+    // Make an empty submit to ensure the buffer's execution serial will not be same as the below
+    // large buffers.
+    wgpu::CommandEncoder encoder = device.CreateCommandEncoder();
+    wgpu::CommandBuffer commandBuffer = encoder.Finish();
+    queue.Submit(1, &commandBuffer);
+
     // Create and touch enough buffers to use the entire budget.
     std::vector<wgpu::Buffer> bufferSet = AllocateBuffers(
         kDirectlyAllocatedResourceSize, kRestrictedBudgetSize / kDirectlyAllocatedResourceSize,