linux-kernel - Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures

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Message-ID: <46BB24CB.1040405@redhat.com>
Date:	Thu, 09 Aug 2007 10:29:31 -0400
From:	Chris Snook <csnook@...hat.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	torvalds@...ux-foundation.org, netdev@...r.kernel.org,
	akpm@...ux-foundation.org, ak@...e.de, heiko.carstens@...ibm.com,
	davem@...emloft.net, schwidefsky@...ibm.com, wensong@...ux-vs.org,
	horms@...ge.net.au, wjiang@...ilience.com, cfriesen@...tel.com,
	zlynx@....org, rpjday@...dspring.com, jesper.juhl@...il.com
Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all
 architectures

Arnd Bergmann wrote:
> On Thursday 09 August 2007, Chris Snook wrote:
>> This patchset makes the behavior of atomic_read uniform by removing the
>> volatile keyword from all atomic_t and atomic64_t definitions that currently
>> have it, and instead explicitly casts the variable as volatile in
>> atomic_read().  This leaves little room for creative optimization by the
>> compiler, and is in keeping with the principles behind "volatile considered
>> harmful".
>>
> 
> Just an idea: since all architectures already include asm-generic/atomic.h,
> why not move the definitions of atomic_t and atomic64_t, as well as anything
> that does not involve architecture specific inline assembly into the generic
> header?
> 
> 	Arnd <><

a) chicken and egg: asm-generic/atomic.h depends on definitions in asm/atomic.h

If you can find a way to reshuffle the code and make it simpler, I personally am 
all for it.  I'm skeptical that you'll get much to show for the effort.

b) The definitions aren't precisely identical between all architectures, so it 
would be a mess of special cases, which gets us right back to where we are now.

	-- Chris
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