Messages in this thread | | | Date | Thu, 30 Mar 2006 19:28:02 -0800 (PST) | From | Christoph Lameter <> | Subject | Re: Synchronizing Bit operations V2 |
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On Fri, 31 Mar 2006, Nick Piggin wrote:
> This has acquire and release, instead of the generic kernel > memory barriers rmb and wmb. As such, I don't think it would > get merged.
Right. From the earlier conversation I had the impression that this is what you wanted.
> > Note that the current semantics for bitops IA64 are broken. Both > > smp_mb__after/before_clear_bit are now set to full memory barriers > > to compensate which may affect performance. > > I think you should fight the fights you can win and get a 90% > solution ;) at any rate you do need to fix the existing routines > unless you plan to audit all callers... > > First, fix up ia64 in 2.6-head, this means fixing test_and_set_bit > and friends, smp_mb__*_clear_bit, and all the atomic operations that > both modify and return a value. > > Then add test_and_set_bit_lock / clear_bit_unlock, and apply them > to a couple of critical places like page lock and buffer lock. > > Is this being planned?
That sounds like a long and tedious route to draw out the pain for a couple of years and add loads of additional macro definitions all over the header files. I'd really like a solution that allows a gradual simplification of the macros and that has clear semantics.
So far it seems that I have not even been able to find the definitions for the proper behavior of memory barriers.
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