437
Subj : Re: Deadlock theorem
To   : comp.programming.threads
From : Joe Seigh
Date : Sun May 01 2005 04:51 pm

On Sun, 1 May 2005 19:18:11 +0200, Uenal Mutlu <520001085531-0001@t-online.de> 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."
>
> Some explanation:
> "Order" in this context means sequence.
> The theorem applies equally well to both sequential and parallel processing
> (ie. threads, tasks, processes, coroutines etc.), and regardless of the number
> of objects one wishes to lock in any of the parallel running units (aka threads).
> That is: the objects designated for locking, and the number of them, can be
> different in each thread; only the locking sequence (order) must be the same in all threads.
>
> (If this theorem is new then I would like to give it the name "Mutlu theorem" :-)
>
>

It's known as hierarchical locking.



-- 
Joe Seigh

When you get lemons, you make lemonade.
When you get hardware, you make software.

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