src/dawn/common/Mutex.h

// Copyright 2023 The Dawn & Tint Authors
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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#ifndef SRC_DAWN_COMMON_MUTEX_H_
#define SRC_DAWN_COMMON_MUTEX_H_

#include <atomic>
#include <mutex>
#include <thread>
#include <utility>

#include "src/dawn/common/Compiler.h"
#include "src/dawn/common/Ref.h"
#include "src/dawn/common/RefCounted.h"
#include "src/utils/assert.h"
#include "src/utils/non_copyable.h"
#include "src/utils/non_movable.h"

namespace dawn {

template <typename MutexT>
class DAWN_MUTEX_CAPABILITY MutexBase : public RefCounted, NonCopyable {
  public:
    template <typename MutexRef>
    struct DAWN_SCOPED_LOCKABLE AutoLockBase : NonCopyable {
        AutoLockBase() : mMutex(nullptr) {}
        explicit AutoLockBase(MutexRef mutex) : mMutex(std::move(mutex)) {
            if (mMutex != nullptr) {
                mMutex->Lock();
            }
        }

        AutoLockBase(AutoLockBase&& other) : mMutex(std::move(other.mMutex)) {
            other.mMutex = nullptr;
        }

        // The move operator conditionally unlocks, and the static thread-safety analysis cannot
        // currently handle conditional locking, so we turn off the analysis here to avoid spurious
        // warnings.
        AutoLockBase& operator=(AutoLockBase&& other) DAWN_NO_THREAD_SAFETY_ANALYSIS {
            if (this != &other) {
                if (mMutex != nullptr) {
                    mMutex->Unlock();
                }
                mMutex = std::move(other.mMutex);
                other.mMutex = nullptr;
            }
            return *this;
        }

        ~AutoLockBase() {
            if (mMutex != nullptr) {
                mMutex->Unlock();
            }
        }

      private:
        MutexRef mMutex;
    };

    // This scoped lock won't keep the mutex alive.
    using AutoLock = AutoLockBase<MutexBase<MutexT>*>;
    // This scoped lock will keep the mutex alive until out of scope.
    using AutoLockAndHoldRef = AutoLockBase<Ref<MutexBase<MutexT>>>;

    ~MutexBase() override = default;

    // This method is only enabled when DAWN_ENABLE_ASSERTS is turned on.
    // Thus it should only be wrapped inside DAWN_ASSERT() macro.
    // i.e. DAWN_ASSERT(mutex.IsLockedByCurrentThread())
    bool IsLockedByCurrentThread() {
#if defined(DAWN_ENABLE_ASSERTS)
        return mOwner.load(std::memory_order_acquire) == std::this_thread::get_id();
#else
        // This is not supported.
        DAWN_UNREACHABLE();
#endif
    }

  protected:
    void Lock() DAWN_EXCLUSIVE_LOCK_FUNCTION {
#if defined(DAWN_ENABLE_ASSERTS)
        auto currentThread = std::this_thread::get_id();
        if constexpr (!std::is_same_v<MutexT, std::recursive_mutex>) {
            DAWN_ASSERT(mOwner.load(std::memory_order_acquire) != currentThread);
        }
#endif  // DAWN_ENABLE_ASSERTS

        mNativeMutex.lock();

#if defined(DAWN_ENABLE_ASSERTS)
        mRecursionStackDepth++;
        mOwner.store(currentThread, std::memory_order_release);
#endif  // DAWN_ENABLE_ASSERTS
    }

    void Unlock() DAWN_UNLOCK_FUNCTION {
#if defined(DAWN_ENABLE_ASSERTS)
        DAWN_ASSERT(IsLockedByCurrentThread());
        if (--mRecursionStackDepth == 0) {
            mOwner.store(std::thread::id(), std::memory_order_release);
        }
#endif  // DAWN_ENABLE_ASSERTS
        mNativeMutex.unlock();
    }

  private:
#if defined(DAWN_ENABLE_ASSERTS)
    std::atomic<std::thread::id> mOwner;
    uint32_t mRecursionStackDepth = 0;
#endif  // DAWN_ENABLE_ASSERTS
    MutexT mNativeMutex;
};

using Mutex = MutexBase<std::mutex>;
using RecursiveMutex = MutexBase<std::recursive_mutex>;

}  // namespace dawn

#endif