Re: [boost] [lockfree] review

25 Aug 2011


      On Thu, 25 Aug 2011 18:19:48 +0600, Alexander Terekhov <terekhov@web.de>  
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