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

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Message-ID: <Pine.LNX.4.64.0708141612590.693@schroedinger.engr.sgi.com>
Date:	Tue, 14 Aug 2007 16:14:21 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Chris Snook <csnook@...hat.com>
cc:	Satyam Sharma <satyam@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-arch@...r.kernel.org, torvalds@...ux-foundation.org,
	netdev@...r.kernel.org, Andrew Morton <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,
	segher@...nel.crashing.org
Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all
 architectures

On Tue, 14 Aug 2007, Chris Snook wrote:

> Because atomic operations are generally used for synchronization, which
> requires volatile behavior.  Most such codepaths currently use an inefficient
> barrier().  Some forget to and we get bugs, because people assume that
> atomic_read() actually reads something, and atomic_write() actually writes
> something.  Worse, these are architecture-specific, even compiler
> version-specific bugs that are often difficult to track down.

Looks like we need to have lock and unlock semantics?

atomic_read()

which has no barrier or volatile implications.

atomic_read_for_lock

	Acquire semantics?


atomic_read_for_unlock

	Release semantics?

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