Atomic updates

[monarch_dodra]

On Tuesday, 22 January 2013 at 10:27:58 UTC, bearophile wrote:
> I have modified a little the code on RosettaCode (no changes in 
> the logic).
>
> monarch_dodra:
>
>> Avoids deadlock.
>>
>> imagine 2 threads:
>> a: from 2 to 5.
>> b: from 5 to 2.
>>
>> If both threads acquire their first lock, then you have a dead 
>> lock, and your program is basically dead.
>>
>> By always locking low first, you avoid the deadlock in a 
>> rather simple but elegant way.
>
> The Go language has four different solutions, one of them is:
> http://rosettacode.org/wiki/Atomic_updates#Lock-free
>
> [SNIP]
>
> Bye,
> bearophile

That's a good point, and I'm sure we could also have a version of 
D that could also do it that way. D has attomic swap operations 
too, AFAIK.

But I was really just answering the original question of "if you 
need 2 locks, why do it that way?".