[Python-ideas] Monitor implementation for the stdlib?

[George Sakkis]

On 10/22/07, Adam Olsen <rhamph at gmail.com> wrote:
> On 10/22/07, George Sakkis <george.sakkis at gmail.com> wrote:
> > On 10/22/07, Adam Olsen <rhamph at gmail.com> wrote:
> >
> > > A method is often *NOT* the
> > > correct granularity to achieve a thread-safe API!  Consider:
> > >
> > > l = ... some "thread-safe" list ...
> > > if l:
> > >     x = l.pop()
> > >
> > > There's two method calls, so you cannot guarantee the object hasn't
> > > changed between them.  I get the impression this is regarded as a
> > > major mistake in Java's extensive use of monitors - plastering locks
> > > everywhere just isn't good enough.
> >
> > My Java's kinda rusty but IIRC one can use synchronized blocks on an
> > object to achieve finer granularity.
>
> You need coarser granularity to achieve correctness in this case.

Well I was talking from the POV of the enclosing method, i.e. something like:

l = ... some "thread-safe" list ...
synchronized(I) {
    if l:
        x = l.pop()
}


George