ordered threading

[Gordon McMillan]

Robin Becker writes:

> In article <000a01bec583$30332b40$769e2299 at tim>, Tim Peters
> <tim_one at email.msn.com> writes

> >[Robin Becker]
> >> I have an unbounded number of worker threads which occasionally require
> >> access to a unique server thread. I can easily mutex access to the
> >> server thread, but is there any obvious/easy way to ensure that the
> >> blocked workers wake up in the right order?
> >
> >No threading system on earth allows specifying the order in which blocked
> >threads will wake up, although some systems (not Python's) allow you to
> >*influence* the order via assorted "priority" gimmicks.

> the workers are HTTP requests in separate threads from Zope I guess.
> I want to serialise access to the time/space hog. I guess it could
> run uniquely in the worker threads ie the locked resource would be
> access to the hog code. I'm not sure that would let me guarantee
> unlocking as there are ways for the worker threads to suicide.

If that's what you want, you don't really need to order the 
unblocking. Just give each thread an input queue protected by a 
Condition. Worker threads put requests on the Hog thread's input 
queue (including a ref to the return queue). If you find that some 
worker threads seem to get better access to the Hog's queue than 
others, a time.sleep(0.001) will probably fix it - since it will 
pretty much force a context switch.


- Gordon