linux-kernel - Re: [PATCH v2 06/32] s390: reuse asm-generic/barrier.h

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Date:	Mon, 4 Jan 2016 22:34:57 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
	linux-arch@...r.kernel.org,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	virtualization@...ts.linux-foundation.org,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	David Miller <davem@...emloft.net>, linux-ia64@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	sparclinux@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-metag@...r.kernel.org, linux-mips@...ux-mips.org,
	x86@...nel.org, user-mode-linux-devel@...ts.sourceforge.net,
	adi-buildroot-devel@...ts.sourceforge.net,
	linux-sh@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
	xen-devel@...ts.xenproject.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 06/32] s390: reuse asm-generic/barrier.h

On Mon, Jan 04, 2016 at 02:20:42PM +0100, Peter Zijlstra wrote:
> On Thu, Dec 31, 2015 at 09:06:30PM +0200, Michael S. Tsirkin wrote:
> > On s390 read_barrier_depends, smp_read_barrier_depends
> > smp_store_mb(), smp_mb__before_atomic and smp_mb__after_atomic match the
> > asm-generic variants exactly. Drop the local definitions and pull in
> > asm-generic/barrier.h instead.
> > 
> > This is in preparation to refactoring this code area.
> > 
> > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> > Acked-by: Arnd Bergmann <arnd@...db.de>
> > ---
> >  arch/s390/include/asm/barrier.h | 10 ++--------
> >  1 file changed, 2 insertions(+), 8 deletions(-)
> > 
> > diff --git a/arch/s390/include/asm/barrier.h b/arch/s390/include/asm/barrier.h
> > index 7ffd0b1..c358c31 100644
> > --- a/arch/s390/include/asm/barrier.h
> > +++ b/arch/s390/include/asm/barrier.h
> > @@ -30,14 +30,6 @@
> >  #define smp_rmb()			rmb()
> >  #define smp_wmb()			wmb()
> >  
> > -#define read_barrier_depends()		do { } while (0)
> > -#define smp_read_barrier_depends()	do { } while (0)
> > -
> > -#define smp_mb__before_atomic()		smp_mb()
> > -#define smp_mb__after_atomic()		smp_mb()
> 
> As per:
> 
>   lkml.kernel.org/r/20150921112252.3c2937e1@...hwide
> 
> s390 should change this to barrier() instead of smp_mb() and hence
> should not use the generic versions.

Thanks Peter!

OK so I will just rename this to __smp_mb__before_atomic and
__smp_mb__after_atomic but keep them around.

I'm not changing these - that's best left to s390 maintainers.

Should I add a TODO comment to change them to barrier so
we don't forget?

-- 
MST
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