lkml.org 
[lkml]   [2015]   [Oct]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [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?


\
 
 \ /
  Last update: 2015-10-28 01:21    [W:0.072 / U:0.120 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site