linux-kernel - Re: [PATCH 2/2] asm-generic: Don't warn that atomic

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Message-ID: <20100428162708.GB2846@Krystal>
Date:	Wed, 28 Apr 2010 12:27:08 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Jamie Lokier <jamie@...reable.org>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Peter Fritzsche <peter.fritzsche@....de>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	Keith M Wesolowski <wesolows@...bazco.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH 2/2] asm-generic: Don't warn that atomic_t is only 24
	bit

* Jamie Lokier (jamie@...reable.org) wrote:
> Mathieu Desnoyers wrote:
> > * Arnd Bergmann (arnd@...db.de) wrote:
> > > On Wednesday 28 April 2010, Peter Fritzsche wrote:
> > > > 32-bit Sparc used to only allow usage of 24-bit of it's atomic_t type.
> > > > This was corrected with linux 2.6.3 when Keith M Wesolowski changed the
> > > > implementation to use the parisc approach of having an array of
> > > > spinlocks to protect the atomic_t.
> > > > 
> > > > These warnings were also removed from the sparc implementation when the
> > > > new implementation was merged in BKrev:402e4949VThdc6D3iaosSFUgabMfvw,
> > > > but the warning still remained in some other places without any
> > > > 24-bit-only atomic_t implementation inside the kernel.
> > > > 
> > > > We should remove these warnings to allow users to rely on the full
> > > > 32-bit range of atomic_t.
> > > > 
> > > > Signed-off-by: Peter Fritzsche <peter.fritzsche@....de>
> > > 
> > > Acked-by: Arnd Bergmann <arnd@...db.de>
> > 
> > AFAIK that was the last architecture imposing limitations below 32 bits
> > on atomic_t.
> > 
> > Acked-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> 
> If the comment's getting removed, it should probably go from here too:
> 
> linux-2.6$ git grep '24' arch/*/include/*/atomic*
> arch/mn10300/include/asm/atomic.h: * useful range of an atomic_t is only 24 bits
> arch/mn10300/include/asm/atomic.h: * useful range of an atomic_t is only 24 bits
> arch/mn10300/include/asm/atomic.h: * Note that the guaranteed useful range of an
> arch/mn10300/include/asm/atomic.h: * Note that the guaranteed useful range of an


How about simply replacing arch/mn10300/include/asm/atomic.h by:

arch/mn10300/include/asm/atomic.h:
#include <asm-generic/atomic.h>

?

This should have been done a while ago. They are almost the same, except for
added cmpxchg*_local() in the asm-generic version (which would benefit to
mn10300).

Thanks,

Mathieu

> 
> -- Jamie

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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