Re: Synchronizing Bit operations V2

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Christoph Lameter wrote:
On Fri, 31 Mar 2006, Nick Piggin wrote:
You acknowledge that you have to fix ia64 to match current semantics
first, right?

Right. I believe I have done so by making both smb_mb_* full barriers.
All bitop and atomic test_and_set, inc_return, etc etc (ie. everything
that modifies the operand and returns something) needs to be a full
barrier before and after too.

Now people seem to be worried about the performance impact that will
have, so I simply suggest that adding two or three new macros for the
important cases to give you a 90% solution.

We could transition some key locations of core code to use _mode bitops
if there are performance problems.

I think Documentation/atomic_ops.txt isn't bad. smp_mb__* really
is a smp_mb, which can be optimised sometimes.

Ok. Then we are on the same page and the solution I presented may be acceptable. I have a new rev here that changes the naming a bit but I think we are okay right?
Not sure, to be honest. I think it is probably something which needs
input from all the other arch people, and Linus, if you intend to use
it to introduce new types of barriers.

SUSE Labs, Novell Inc.
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