I can't get RLock to work (warning, the following code is pretty long)

grocery_stocker cdalten at gmail.com
Fri Apr 10 18:03:56 CEST 2009


On Apr 10, 8:39 am, Peter Otten <__pete... at web.de> wrote:
> grocery_stocker wrote:
> > On Apr 10, 6:48 am, Peter Otten <__pete... at web.de> wrote:
> >> grocery_stocker wrote:
> >> > When I run the following...
>
> >> > #!/usr/bin/python
>
> >> > import time
> >> > import thread
> >> > import threading
>
> >> > def get_first_part(string, lock, sleeptime, *args):
> >> >         global counter
> >> >         lock.acquire()
> >> >         try:
> >> >                 counter = counter + 1
> >> >                 data = counter
> >> >                 print "%s value is %d" % (string, counter)
> >> >                 time.sleep(sleeptime)
> >> >         finally:
> >> >                 lock.release()
> >> >         return data
> >> > def get_both_parts(string, lock, sleeptime, *args):
> >> >         global first, second
> >> >         lock.acquire()
> >> >         try:
> >> >                 first = get_first_part()
> >> >                 second = get_second_part()
> >> >                 print "%s values are %d and %d" % (string, first,
> >> > second)
> >> >                 time.sleep(sleeptime)
> >> >         finally:
> >> >                 lock.release()
> >> >                 return first, second
> >> > How come RLock isn't working in this example?
>
> >> When get_both_parts() acquires the lock it invokes get_first_part() which
> >> tries to acquire the lock. This fails because get_both_parts() does not
> >> release the lock until after get_first_part() has finished...
>
> >> Peter
>
> > i thought a Rlock() (vs a Lock()) was suspposed to get around this
> > kind of a problem.
>
> Oops, yes. In get_both_parts() try calling get_first_part/get_second_part()
> with the three necessary arguments...
>

Doh. I knew that. I really did.




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