Messages in this thread | | | Date | Tue, 27 Oct 2015 23:37:44 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 3/4] x86,asm: Re-work smp_store_mb() |
| |
On Wed, Oct 28, 2015 at 06:33:56AM +0900, Linus Torvalds wrote: > On Wed, Oct 28, 2015 at 4:53 AM, Davidlohr Bueso <dave@stgolabs.net> wrote: > > > > Note that this might affect callers that could/would rely on the > > atomicity semantics, but there are no guarantees of that for > > smp_store_mb() mentioned anywhere, plus most archs use this anyway. > > Thus we continue to be consistent with the memory-barriers.txt file, > > and more importantly, maintain the semantics of the smp_ nature. >
> So with this patch, the whole thing becomes pointless, I feel. (Ok, so > it may have been pointless before too, but at least before this patch > it generated special code, now it doesn't). So why carry it along at > all?
So I suppose this boils down to if: XCHG ends up being cheaper than MOV+FENCE.
PeterA, any idea?
| |