Subj : Re: Deadlock theorem
To   : comp.programming.threads
From : Uenal Mutlu
Date : Tue May 03 2005 08:50 pm

"David Holmes" wrote
> "Uenal Mutlu" wrote
> > Theorem:
> >    a) "There will be no deadlock if the objects are locked in the same
> order."
> >    b) "Unlocking can be done in any order."
....
> deadlock occurs if you have a cyclic dependency in the lock acquisition
> order:
>   - thread 1: acquire A try to acquire B
>  - thread 2: acquire B try to acquire A
>
> This is the defining property of deadlock.
>
> Every text that discusses deadlock discusses the ways to avoid deadlock.
> Acquiring your locks in a consistent order is one such technique.

Sure, I just tried to formulate a law and to apply it practically, esp.
for thread programming.

> This solution has been known ever since "locking" (or historically it was
> probably described in terms of semaphore operations) has existed.

I wonder why they used the term "semaphore operations" whereas
"order of locking" would very much suffice.

.