Re: Synchronizing Bit operations V2

[Nick Piggin]

Christoph Lameter wrote:
> On Fri, 31 Mar 2006, Chen, Kenneth W wrote:
>
>
> > > I think we could say that lock semantics are different from barriers. They 
> > > are more like acquire and release on IA64. The problem with smb_mb_*** is 
> > > that the coder *explicitly* requested a barrier operation and we do not 
> > > give it to him.
> >
> > I was browsing sparc64 code and it defines:
> >
> > include/asm-sparc64/bitops.h:
> > #define smp_mb__after_clear_bit()      membar_storeload_storestore()
> >
> > With my very naïve knowledge of sparc64, it doesn't look like a full barrier.
> > Maybe sparc64 is broken too ...
>
>
> Dave, how does sparc64 handle this situation?

It looks like sparc64 always expects paired smp_mb__* operations,
before and after the clear_bit.

--
SUSE Labs, Novell Inc.
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