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

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Message-ID: <617E1C2C70743745A92448908E030B2A02322189@scsmsx411.amr.corp.intel.com>
Date:	Thu, 16 Aug 2007 14:08:52 -0700
From:	"Luck, Tony" <tony.luck@...el.com>
To:	"Chris Snook" <csnook@...hat.com>,
	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
Cc:	"Herbert Xu" <herbert@...dor.apana.org.au>,
	"Paul Mackerras" <paulus@...ba.org>,
	"Satyam Sharma" <satyam@...radead.org>,
	"Christoph Lameter" <clameter@....com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"Stefan Richter" <stefanr@...6.in-berlin.de>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	<linux-arch@...r.kernel.org>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Netdev" <netdev@...r.kernel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>, <ak@...e.de>,
	<heiko.carstens@...ibm.com>, "David Miller" <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>, <segher@...nel.crashing.org>
Subject: RE: [PATCH 0/24] make atomic_read() behave consistently across all architectures

>> 6674:   while (atomic_read(&j->DSPWrite) > 0)
>> 6675-           atomic_dec(&j->DSPWrite);
>
> If the maintainer of this code doesn't see a compelling reason to add 
> cpu_relax() in this loop, then it should be patched.

Shouldn't it be just re-written without the loop:

	if ((tmp = atomic_read(&j->DSPWrite)) > 0)
		atomic_sub(&j->DSPWrite, tmp);

Has all the same bugs, but runs much faster :-)

-Tony
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