src/dawn/native/metal/QueueMTL.h

// Copyright 2018 The Dawn & Tint Authors
//
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#ifndef SRC_DAWN_NATIVE_METAL_QUEUEMTL_H_
#define SRC_DAWN_NATIVE_METAL_QUEUEMTL_H_

#import <Metal/Metal.h>
#include <map>

#include "dawn/common/MutexProtected.h"
#include "dawn/common/SerialMap.h"
#include "dawn/native/EventManager.h"
#include "dawn/native/Queue.h"
#include "dawn/native/SystemEvent.h"
#include "dawn/native/metal/CommandRecordingContext.h"

namespace dawn::native::metal {

class Device;
struct ExternalImageMTLSharedEventDescriptor;

class Queue final : public QueueBase {
  public:
    static ResultOrError<Ref<Queue>> Create(Device* device, const QueueDescriptor* descriptor);

    CommandRecordingContext* GetPendingCommandContext(SubmitMode submitMode = SubmitMode::Normal);
    MaybeError SubmitPendingCommandBuffer();
    void WaitForCommandsToBeScheduled();
    void ExportLastSignaledEvent(ExternalImageMTLSharedEventDescriptor* desc);

    Ref<SystemEvent> CreateWorkDoneSystemEvent(ExecutionSerial serial);
    ResultOrError<bool> WaitForQueueSerial(ExecutionSerial serial, Nanoseconds timeout) override;

  private:
    Queue(Device* device, const QueueDescriptor* descriptor);
    ~Queue() override;

    MaybeError Initialize();
    void UpdateWaitingEvents(ExecutionSerial completedSerial);

    MaybeError SubmitImpl(uint32_t commandCount, CommandBufferBase* const* commands) override;
    bool HasPendingCommands() const override;
    MaybeError SubmitPendingCommands() override;
    ResultOrError<ExecutionSerial> CheckAndUpdateCompletedSerials() override;
    void ForceEventualFlushOfCommands() override;
    MaybeError WaitForIdleForDestruction() override;
    void DestroyImpl() override;

    NSPRef<id<MTLCommandQueue>> mCommandQueue;
    CommandRecordingContext mCommandContext;

    // mLastSubmittedCommands will be accessed in a Metal schedule handler that can be fired on
    // a different thread so we guard access to it with a mutex.
    std::mutex mLastSubmittedCommandsMutex;
    NSPRef<id<MTLCommandBuffer>> mLastSubmittedCommands;

    // The completed serial is updated in a Metal completion handler that can be fired on a
    // different thread, so it needs to be atomic.
    std::atomic<uint64_t> mCompletedSerial;

    // This mutex must be held to access mWaitingEvents (which may happen in a Metal driver
    // thread).
    // TODO(crbug.com/dawn/2065): If we atomically knew a conservative lower bound on the
    // mWaitingEvents serials, we could avoid taking this lock sometimes. Optimize if needed.
    // See old draft code: https://dawn-review.googlesource.com/c/dawn/+/137502/29
    MutexProtected<SerialMap<ExecutionSerial, Ref<SystemEvent>>> mWaitingEvents;

    // A shared event that can be exported for synchronization with other users of Metal.
    // MTLSharedEvent is not available until macOS 10.14+ so use just `id`.
    NSPRef<id> mMtlSharedEvent = nullptr;
};

}  // namespace dawn::native::metal

#endif  // SRC_DAWN_NATIVE_METAL_QUEUEMTL_H_