linux-kernel - Re: [PATCH 11/23] make atomic_read() and atomic

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Message-ID: <alpine.LFD.0.999.0708231310430.30176@woody.linux-foundation.org>
Date:	Thu, 23 Aug 2007 13:12:32 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Segher Boessenkool <segher@...nel.crashing.org>
cc:	Hirokazu Takata <takata@...ux-m32r.org>,
	"Robert P. J. Day" <rpjday@...dspring.com>,
	paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	"Luck, Tony" <tony.luck@...el.com>, akpm@...ux-foundation.org,
	linux-arch@...r.kernel.org, Chris Snook <csnook@...hat.com>,
	Chris Friesen <cfriesen@...tel.com>
Subject: Re: [PATCH 11/23] make atomic_read() and atomic_set() behavior
 consistent on m32r



On Thu, 23 Aug 2007, Segher Boessenkool wrote:
> 
> This simply isn't true.  The compiler *can* combine asm stuff:

Please Segher, just shut up.

The combining, which I've mentioned *multiple*times* is

	if (atomic_read(&x) <= 1)

and dammit, if that doesn't result in a *single* instruction, the code 
generation is pure and utter crap.

It should result in

	cmpl $1,offset(reg)

and nothing else. And there is no way in hell you are doing that with 
"atomic_read()" being inline asm.

So can you now just go away?

		Linus
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