445
Subj : Re: Deadlock theorem
To   : comp.programming.threads
From : Peter Koch Larsen
Date : Mon May 02 2005 02:40 pm


"Uenal Mutlu" <520001085531-0001@t-online.de> skrev i en meddelelse 
news:d548ah$j2u$05$1@news.t-online.com...
> "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.

/Peter

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