On Mon, Jun 21, 2010 at 10:40 AM, erik quanstrom <[email protected]>wrote:
> void
> lock(ulong *l)
> {
> ulong old;
> ushort next, owner;
>
> old = _xadd(l, 1);
> for(;;){
> next = old;
> owner = old>>16;
> old = *l;
> if(next == owner)
> break;
> }
> }
>
> void
> unlock(ulong *l)
> {
> _xadd(l, 1<<16);
> }
Sure, that's reasonable in C; (i wasn't sure how to do it in asm for 8_a_,
that was what I was asking about). Just also remember to provide xadd; the
distribution 8a and 8l didn't support it last I checked.
Just another observation, we can bypass the load of old in the uncontended
case if we reverse old = *l and the compare/break in lock.
Anyway, thoughts on this lock?
-- vs
