Messages in this thread | | | Date | Thu, 26 Sep 2013 16:53:31 +0100 | From | Will Deacon <> | Subject | Re: [RFC PATCH 1/4] asm-generic: cmpxchg: implement dummy cmpxchg64_relaxed operation |
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On Thu, Sep 26, 2013 at 04:34:04PM +0100, Linus Torvalds wrote: > On Thu, Sep 26, 2013 at 8:13 AM, Will Deacon <will.deacon@arm.com> wrote: > > > > This patch implements a dummy implementation for asm-generic, falling > > back to the usual cmpxchg64 code. > > I don't like the "let's add dummy operations for everybody who doesn't > care" when it is this specialized. > > I'd much rather just add a single > > #ifndef cmpxchg64_relaxed > # define cmpxchg64_relaxed cmpxchg64 > #endif > > to the LOCKREF code, and then ARM (and others) can define it as they wish.
Okey doke.
> And *if* anybody else ever realizes that they want this outside of the > lockref code, let's look at doing that then. Right now I don't know of > any users, and I'd be leery of people using this willy-nilly, because > very few people really understand memory ordering.
Agreed, and I really doubt there are many cases where the cmpxchg hazarding works out nicely so as to obviate the need for memory barriers.
I'll send a revised patch.
Cheers,
Will
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