On Mon, Nov 23, 2009 at 12:26 PM, Anthony Williams <anthony.ajw@gmail.com> wrote:
You don't need a new event. If the event is set it means "check the status". So thread enters call_once. Sees status is "running" and waits on the event. When the event is set it wakes and checks status. If status is complete, we're done. If status is running, wait for the same event again. If status is "not done", set it to running, reset the event and run the function. On completion, set status to "complete" and set the event. On exception, set status to "not done" and set the event.
I'll code it up.
Anthony --
It is worth giving it a try, but we went down that road in pthreads-win32. I think the hard part is the 'reset the event' step. There were problems with whether the event should be manual or auto-reset, and with the 3rd thread in looping without waiting, etc. IIRC manual means you have a hard time knowing when to reset (ie did everyone or ANYONE wait yet - you could close too early), auto-reset meant that each 'waker' needed to wake the next one, etc. I can't remember what was really bad about chaining the waking of the waiters. Maybe it just felt a bit queasy. But I have a lot of faith in your work, so you may very well find something that we missed. Tony