Op 2005-03-29, Paul Rubin schreef <http>: > Antoon Pardon <[EMAIL PROTECTED]> writes: >> I'm not going to call my solution simple, but it wastes very few >> cycles. if no thread is blocked on a lock, the select will just >> block until that changes. No need for some kind of polling loop. > > I think I understand. My original idea was to use a heapq to be able > to know exactly when the next pending timeout is due, and usleep for > long enough to wake up at just the right time. Then you service the > timeout, pop the heap to find when the next timeout after that is, and > usleep again. No polling loops and no pipe. But it could be that > someone inserts a new timeout while you're sleeping, that's due before > you're scheduled to wake up. Your pipe scheme takes care of that, > since any thread can write to the pipe and wake up the blocked thread > at any time.
Right, that is the idea. > Really, the culprit here is the weak signalling scheme in Python. > There needs to be a way to send signals to threads, or raise > asynchronous exceptions in them. There's been some discussion in > sourceforge about that, but the issues involved are complex. Well I have raised this issue before and as far as I understand, the big problem seems to be the various kind of behaviour you can get depending on what platform you are working, so writing a module so that python programs behave the same on various platforms seems a hell of a job. So I decided not to pester the python people for this kind of functionality, although I would very much like to have it. I have been playing with the C-API and have somekind of class that allows one thread to raise an excetion in an other but that wouldn't be a solution here, since the raised exception will not manifest itself while the thread is in a C-function. > I think the best bet for the short term is handling it at the C level, > with sigalarm. Another way is to have chained sigalarm handlers in > the main thread. Possible, but I don't have the time to investigate that possibility now. -- Antoon Pardon -- http://mail.python.org/mailman/listinfo/python-list
