linux-kernel - Re: [PATCH v2 20/32] metag: define __smp

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Date:	Mon, 11 Jan 2016 13:10:54 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	James Hogan <james.hogan@...tec.com>
Cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.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, Ingo Molnar <mingo@...nel.org>,
	Davidlohr Bueso <dbueso@...e.de>,
	Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH v2 20/32] metag: define __smp_xxx

On Tue, Jan 05, 2016 at 12:09:30AM +0000, James Hogan wrote:
> Hi Michael,
> 
> On Thu, Dec 31, 2015 at 09:08:22PM +0200, Michael S. Tsirkin wrote:
> > This defines __smp_xxx barriers for metag,
> > for use by virtualization.
> > 
> > smp_xxx barriers are removed as they are
> > defined correctly by asm-generic/barriers.h
> > 
> > Note: as __smp_XX macros should not depend on CONFIG_SMP, they can not
> > use the existing fence() macro since that is defined differently between
> > SMP and !SMP.  For this reason, this patch introduces a wrapper
> > metag_fence() that doesn't depend on CONFIG_SMP.
> > fence() is then defined using that, depending on CONFIG_SMP.
> 
> I'm not a fan of the inconsistent commit message wrapping. I wrap to 72
> columns (although I now notice SubmittingPatches says to use 75...).
> 
> > 
> > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> > Acked-by: Arnd Bergmann <arnd@...db.de>
> > ---
> >  arch/metag/include/asm/barrier.h | 32 +++++++++++++++-----------------
> >  1 file changed, 15 insertions(+), 17 deletions(-)
> > 
> > diff --git a/arch/metag/include/asm/barrier.h b/arch/metag/include/asm/barrier.h
> > index b5b778b..84880c9 100644
> > --- a/arch/metag/include/asm/barrier.h
> > +++ b/arch/metag/include/asm/barrier.h
> > @@ -44,13 +44,6 @@ static inline void wr_fence(void)
> >  #define rmb()		barrier()
> >  #define wmb()		mb()
> >  
> > -#ifndef CONFIG_SMP
> > -#define fence()		do { } while (0)
> > -#define smp_mb()        barrier()
> > -#define smp_rmb()       barrier()
> > -#define smp_wmb()       barrier()
> > -#else
> 
> !SMP kernel text differs, but only because of new presence of unused
> metag_fence() inline function. If I #if 0 that out, then it matches, so
> thats fine.
> 
> > -
> >  #ifdef CONFIG_METAG_SMP_WRITE_REORDERING
> >  /*
> >   * Write to the atomic memory unlock system event register (command 0). This is
> > @@ -60,26 +53,31 @@ static inline void wr_fence(void)
> >   * incoherence). It is therefore ineffective if used after and on the same
> >   * thread as a write.
> >   */
> > -static inline void fence(void)
> > +static inline void metag_fence(void)
> >  {
> >  	volatile int *flushptr = (volatile int *) LINSYSEVENT_WR_ATOMIC_UNLOCK;
> >  	barrier();
> >  	*flushptr = 0;
> >  	barrier();
> >  }
> > -#define smp_mb()        fence()
> > -#define smp_rmb()       fence()
> > -#define smp_wmb()       barrier()
> > +#define __smp_mb()        metag_fence()
> > +#define __smp_rmb()       metag_fence()
> > +#define __smp_wmb()       barrier()
> >  #else
> > -#define fence()		do { } while (0)
> > -#define smp_mb()        barrier()
> > -#define smp_rmb()       barrier()
> > -#define smp_wmb()       barrier()
> > +#define metag_fence()		do { } while (0)
> > +#define __smp_mb()        barrier()
> > +#define __smp_rmb()       barrier()
> > +#define __smp_wmb()       barrier()
> 
> Whitespace is now messed up. Admitedly its already inconsistent
> tabs/spaces, but it'd be nice if the definitions at least still all
> lined up. You're touching all the definitions which use spaces anyway,
> so feel free to convert them to tabs while you're at it.
> 
> Other than those niggles, it looks sensible to me:
> Acked-by: James Hogan <james.hogan@...tec.com>
> 
> Cheers
> James

Thanks!

I did this in my tree (replaced spaces with tabs in the new
definitions); not reposting just because of this change.

> >  #endif
> > +
> > +#ifdef CONFIG_SMP
> > +#define fence() metag_fence()
> > +#else
> > +#define fence()		do { } while (0)
> >  #endif
> >  
> > -#define smp_mb__before_atomic()	barrier()
> > -#define smp_mb__after_atomic()	barrier()
> > +#define __smp_mb__before_atomic()	barrier()
> > +#define __smp_mb__after_atomic()	barrier()
> >  
> >  #include <asm-generic/barrier.h>
> >  
> > -- 
> > MST
> >