linux-kernel - Re: [PATCH v2 17/32] arm: define __smp

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Message-ID: <20160103110158-mutt-send-email-mst@redhat.com>
Date:	Sun, 3 Jan 2016 11:12:44 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
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>,
	Tony Lindgren <tony@...mide.com>,
	Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH v2 17/32] arm: define __smp_xxx

On Sat, Jan 02, 2016 at 11:24:38AM +0000, Russell King - ARM Linux wrote:
> On Thu, Dec 31, 2015 at 09:07:59PM +0200, Michael S. Tsirkin wrote:
> > This defines __smp_xxx barriers for arm,
> > for use by virtualization.
> > 
> > smp_xxx barriers are removed as they are
> > defined correctly by asm-generic/barriers.h
> > 
> > This reduces the amount of arch-specific boiler-plate code.
> > 
> > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> > Acked-by: Arnd Bergmann <arnd@...db.de>
> 
> In combination with patch 14, this looks like it should result in no
> change to the resulting code.
> 
> Acked-by: Russell King <rmk+kernel@....linux.org.uk>
> 
> My only concern is that it gives people an additional handle onto a
> "new" set of barriers - just because they're prefixed with __*
> unfortunately doesn't stop anyone from using it (been there with
> other arch stuff before.)
> 
> I wonder whether we should consider making the smp memory barriers
> inline functions, so these __smp_xxx() variants can be undef'd
> afterwards, thereby preventing drivers getting their hands on these
> new macros?

That'd be tricky to do cleanly since asm-generic depends on
ifndef to add generic variants where needed.

But it would be possible to add a checkpatch test for this.


> -- 
> RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
> according to speedtest.net.
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