RE: Synchronizing Bit operations V2

[Chen, Kenneth W]

Christoph Lameter wrote on Thursday, March 30, 2006 4:55 PM
> > We are talking about arch specific implementation of clear_bit and smp_mb_*.
> > Yes, for generic code, clear_bit has no implication of memory ordering, but
> > for arch specific code, one should optimize those three functions with the
> > architecture knowledge of exactly what's happening under the hood.
> 
> Arch specific code should make this explicit too and not rely on implied 
> semantics. Otherwise one has to memorize that functions have to work with 
> different semantics in arch code and core code which makes the source 
> code difficult to maintain.

I don't know whether we are talking about the same thing: I propose for ia64:
clear_bit to have release semantic, smp_mb__before_clear_bit will be a noop, smp_mb_after_clear_bit will be a smp_mb().

Caller are still required to use smp_mb__before_clear_bit if it requires, on
ia64, that function will simply be a noop.

- Ken
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