Method ResetPresentTrackingData

PresentData/PresentMonTraceConsumer.cpp:3503–3623

}

void PMTraceConsumer::ResetPresentTrackingData(bool shrink) {

    // Disable any future processing first
    SetEventProcessingEnabled(false);

    // Wait for in-flight event handlers to drain so we can safely clear the
    // tracking maps without taking a mutex on every ETW event. This is only
    // meaningful when provider-toggle mode is enabled and EventProcessingScope
    // is active in the ETW callbacks.
    auto const& shim = GetWaitOnAddressShim();

    ULONGLONG const startMs = ::GetTickCount64();
    DWORD const timeoutMs = 2000;

    while (::InterlockedCompareExchange(&mEventProcessingInFlight, 0, 0) != 0) {
        ULONGLONG elapsed = ::GetTickCount64() - startMs;
        if (elapsed >= timeoutMs) {
            pmlog_warn("Timed out waiting for event processing to quiesce; skipping present tracking reset");
            return;
        }
        DWORD remaining = timeoutMs - (DWORD)elapsed;
        if (shim.Available()) {
            LONG expected = ::InterlockedCompareExchange(&mEventProcessingInFlight, 0, 0);
            if (expected != 0) {
                // Wait until the value at the address changes from 'expected'.
                // Spurious wakeups are possible; loop re-check handles it.
                shim.Wait(&mEventProcessingInFlight, &expected, sizeof(expected), remaining);
            }
        }
        else {
            // Win7 fallback
            ::Sleep(1);
        }
    }

    pmlog_info("Present tracking reset: Event processing quiesced; proceeding with present tracking reset shrink ="
        + std::to_string(shrink));
    // Now it is safe to clear the state
    {
        std::lock_guard<std::mutex> lock(mPresentEventMutex);
        // Clear rings and counters
        for(auto& p : mTrackedPresents) {
            p.reset();
        }
        for(auto& p : mCompletedPresents) {
            p.reset();
        }
        mNextFreeRingIndex = 0;
        mCompletedIndex = 0;
        mCompletedCount = 0;
        mReadyCount = 0;
        mNumOverflowedPresents = 0;

        // We need to see a completed present again after the providers restart
        mHasCompletedAPresent = false;

        // DWM tracking
        mPresentsWaitingForDWM.clear();