Subj : Re: lockless low-overhead 'pipes' (w/semaphores)
To   : comp.programming.threads
From : Chris Thomasson
Date : Fri Apr 22 2005 08:24 am

> Apart from the SSE string stuff, on IA32 (compiler reordering aside
> for a moment), loads have acquire semantics, stores have release
> semantics, and interlocked stuff is fully-fenced (compound acquire +
> release semantics).

Right. The OP should also understand that critical sections can overlap:


1: Lock( &l1 );
2: l1_dat += 111;
3: Unlock( &l1 );

4: Lock( &l2 );
5: l2_dat += 222;
6: Unlock( &l2 );

Can be legitimately be reordered to:

4: Lock( &l2 );
5: l2_dat += 222;
1: Lock( &l1 );
2: l1_dat += 111;
6: Unlock( &l2 );
3: Unlock( &l1 );


on IA32's...

.