Re: [PATCH] locking/atomics/powerpc: Move cmpxchg helpers to asm/cmpxchg.h and define the full set of cmpxchg APIs

From: Ingo Molnar
Date: Mon May 07 2018 - 02:50:32 EST



* Boqun Feng <boqun.feng@xxxxxxxxx> wrote:

>
>
> On Sun, May 6, 2018, at 8:11 PM, Ingo Molnar wrote:
> >
> > * Boqun Feng <boqun.feng@xxxxxxxxx> wrote:
> >
> > > > The only change I made beyond a trivial build fix is that I also added the release
> > > > atomics variants explicitly:
> > > >
> > > > +#define atomic_cmpxchg_release(v, o, n) \
> > > > + cmpxchg_release(&((v)->counter), (o), (n))
> > > > +#define atomic64_cmpxchg_release(v, o, n) \
> > > > + cmpxchg_release(&((v)->counter), (o), (n))
> > > >
> > > > It has passed a PowerPC cross-build test here, but no runtime tests.
> > > >
> > >
> > > Do you have the commit at any branch in tip tree? I could pull it and
> > > cross-build and check the assembly code of lib/atomic64_test.c, that way
> > > I could verify whether we mess something up.
> > >
> > > > Does this patch look good to you?
> > > >
> > >
> > > Yep!
> >
> > Great - I have pushed the commits out into the locking tree, they can be
> > found in:
> >
> > git fetch git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
> > locking/core
> >
>
> Thanks! My compile test told me that we need to remove the definitions of
> atomic_xchg and atomic64_xchg in ppc's asm/atomic.h: they are now
> duplicate, and will prevent the generation of _release and _acquire in the
> new logic.
>
> If you need a updated patch for this from me, I could send later today.
> (I don't have a handy environment for patch sending now, so...)

That would be cool, thanks! My own cross-build testing didn't trigger that build
failure.

> Other than this, the modification looks fine, the lib/atomic64_test.c
> generated the same asm before and after the patches.

Cool, thanks for checking!

Thanks,

Ingo