[M3devel] win32 AlertPause polls instead of one big wait?

[Tony Hosking]

Can you get spurious wakeups with those Windows calls?

On 11 Dec 2009, at 09:05, Jay K wrote:

> Anyone know why Win32 AlertPause uses a polling loop instead of just one wait?
>  
>  
> I'm not sure this is going to work out, but:
>   I'm "rewriting" stuff to use a separate event for alerting.
>   alertable goes away
>   There will be two events: 
>     waitEvent, for condition variables
>     alertEvent, for alerting 
>  
>  
> roughly speaking:
>  
>  
> AlertPause: WaitForSingleObject(alertEvent)
> AlertWait:
>    alerted := WaitForMultipleObjects({alertEvent, waitEvent}) == WAIT_OBJECT_0)
> Alert(t): SetEvent(t.alertEvent);
> TestAlert: alerted := WaitForSingleObject(alertEvent, 0);
>  
>  
> It seems simple enough.
> That shows all the ingredients.
> That'll eliminate a lot of the global locking.
> And then one "last" iteration to use the Java code for condition variables and the global lock will be gone.
> You can't just use the Java code because it doesn't include alertability.
> You can't, I believe, draw a parallel to the pthreads code, because the Java code doesn't maintain a wait list with a mutex.
> The waiter/tickets/counter stuff is pretty clever -- I don't understand it yet..
>  
>  
>  - Jay

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