Closing timers handle from the working thread

Question

best way to ask a question is to first show an example:

this is how i create a timer in c++:

        if (FALSE == CreateTimerQueueTimer(&m_hSampleStarvationTimer,
                                            m_hSampleStarvationTimerQueue,
                                            (WAITORTIMERCALLBACK)TsSampleStarvationTimeBomb_Static,
                                            (LPVOID)this,
                                            dwDueTime,
                                            0,
                                            WT_EXECUTEONLYONCE))

once the following callback is triggered(TsSampleStarvationTimeBomb_Static), i try to kill both the queue handle and timer's handle inside that particular thread.

void CALLBACK CCaptureChannel::TsSampleStarvationTimeBomb_Static(LPVOID lpArg, BOOLEAN TimerOrWaitFired)
    {
        HRESULT hr;
        BOOL    bHandleDeletion          = FALSE;
        CCaptureChannel* pCaptureChannel = (CCaptureChannel*)lpArg;

        ATLASSERT(pCaptureChannel);

        bHandleDeletion = DeleteTimerQueueTimer(pCaptureChannel->m_hSampleStarvationTimerQueue, pCaptureChannel->m_hSampleStarvationTimer, NULL);
        bHandleDeletion = DeleteTimerQueue(pCaptureChannel->m_hSampleStarvationTimerQueue);

my question is: is it valid? i read over MSDN that the following deletion functions may return i/o errors which shouldn't concern me too much. their termination will be executed once the callback thread turns signled, automatically.

am i right? Thanks!

The SDK docs warns about deadlocks doing this. Consider DeleteTimerQueueEx() instead. — Hans Passant, Sep 12 '12 at 12:07
Im not sure im following this, once the Callback function(async) is done executing its code, what will happen to the timer's handle? will it be automatically released? or do i need to call Delete/Cancel function to free it? — igal k, Sep 12 '12 at 14:07

score 2 · Accepted Answer · answered Sep 12 '12 at 17:12

2

DeleteTimerQueueEx will cancel and delete all timers associated with the queue as soon as all timer callbacks complete, so a single call to DeleteTimerQueueEx will suffice. You don't need the call to DeleteTimerQueueTimer. If you call it from within the callback as you currently have in your code, you must pass NULL as the CompletionEvent parameter to avoid deadlocking.

answered Sep 12 '12 at 17:12

Carey Gregory

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If im not mistaken, DeleteTimerQueueEx also cancels and deletes the TimerQueue aswell. – igal k Sep 13 '12 at 07:30
Yes, as its name indicates. So one call to DeleteTimerQueueEx is all you should be using, as I indicated in my answer. – Carey Gregory Sep 13 '12 at 17:36

Closing timers handle from the working thread

1 Answers1