Subj : Re: Deadlock theorem
To   : comp.programming.threads
From : Uenal Mutlu
Date : Mon May 02 2005 05:03 pm

"Peter Koch Larsen" wrote
> "Uenal Mutlu" skrev
> > "Joe Seigh" wrote
> >>
> >> Releasing a lock doesn't block, so there's no requirement on any
> >> release order, though you can't reacquire the lock if you hold locks
> >> further down in the hierarchy without releasing those locks first.
> >
> > Do you mean that the following case is not possible with hierarchical
> > locking?
> > o1.Lock();
> > o2.Lock();
> > o3.Lock();
> > o1.Unlock()
> > o2.Unlock();
> > o1.Lock();
> >
> > With my method this is possible. And this also shows that the
> > methods indeed aren't the same.
> >
> >
> What do you mean? Let us test your solution:
> Thread 1:
> o1.Lock();
> o2.Lock();
> o3.Lock();
> o1.Unlock()
> o2.Unlock();
> >>  context switch
>
> Thread 2:
> o1.Lock();
> o2.Lock();
> o3.Lock(); => waits for unlock by thread 1
>
> Thread 1 resumes:
> o1.Lock(); => waits for unlock by thread 2
>
> A nice and simple deadlock.

Of course you are right. I'm aware of the deadlock when there
is more than 1 thread. The purpose of the code was just to
show one of the differences between the definition of hierarchical
locking and my method.

.