src/dawn/native/WaitListEvent.cpp

// Copyright 2025 The Dawn & Tint Authors
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#include "dawn/native/WaitListEvent.h"

#include <array>

#include "dawn/common/Ref.h"

namespace dawn::native {

WaitListEvent::WaitListEvent(uint64_t requiredSignalCount)
    : mRemainingSignalCount(requiredSignalCount) {
    DAWN_ASSERT(mRemainingSignalCount > 0);
}
WaitListEvent::~WaitListEvent() = default;

bool WaitListEvent::IsSignaled() const {
    return mRemainingSignalCount.load(std::memory_order_acquire) == 0;
}

void WaitListEvent::Signal() {
    uint64_t prevSignalCount = mRemainingSignalCount.fetch_sub(1, std::memory_order_release);
    DAWN_ASSERT(prevSignalCount != 0);
    if (prevSignalCount == 1) {
        std::lock_guard<std::mutex> lock(mMutex);
        for (SyncWaiter* w : std::move(mSyncWaiters)) {
            {
                std::lock_guard<std::mutex> waiterLock(w->mutex);
                w->waitDone = true;
            }
            w->cv.notify_all();
        }
        for (auto& sender : std::move(mAsyncWaiters)) {
            std::move(sender).Signal();
        }
    }
}

bool WaitListEvent::Wait(Nanoseconds timeout) {
    bool ready = false;
    std::array<std::pair<Ref<WaitListEvent>, bool*>, 1> events{{{this, &ready}}};
    return WaitListEvent::WaitAny(events.begin(), events.end(), timeout);
}

SystemEventReceiver WaitListEvent::WaitAsync() {
    std::lock_guard<std::mutex> lock(mMutex);
    if (IsSignaled()) {
        return SystemEventReceiver::CreateAlreadySignaled();
    }
    SystemEventPipeSender sender;
    SystemEventReceiver receiver;
    std::tie(sender, receiver) = CreateSystemEventPipe();
    mAsyncWaiters.push_back(std::move(sender));
    return receiver;
}

}  // namespace dawn::native