Re: [boost] [lockfree] review

Subject: Re: [boost] [lockfree] review
From: Ilya Sokolov (ilyasokol_at_[hidden])
Date: 2011-08-25 09:27:00

On Thu, 25 Aug 2011 18:19:48 +0600, Alexander Terekhov <terekhov_at_[hidden]>  
wrote:>
> Ilya Sokolov wrote:
>> int x = 0;
>> int y = 0;
>> int r1, r2;
>> mutex mx, my;
>>
>> // Thread 1:
>> mx.lock();
>> x = 1;
>> mx.unlock();
>>
>> my.lock();
>> r1 = y;
>> my.unlock();
>>
>> // Thread 2:
>> my.lock();
>> y = 1;
>> my.unlock();
>>
>> mx.lock();
>> r2 = x;
>> mx.unlock();
>>
>> Now, it is possible that r1 == r2 == 0, ...
>
> Nope, it is impossible. Same as with
>
>   // Thread 1:
>   multi_lock(mx, my); // deadlock free
>   r1 = y;
>   x = 1;
>   mx.unlock();
>   my.unlock();
>
>   // Thread 2:
>   multi_lock(my, mx); // deadlock free
>   r2 = x;
>   y = 1;
>   my.unlock();
>   mx.unlock();

Doh! Should have done that myself.
Sorry for the noise