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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20070820224859.GA16162@flint.arm.linux.org.uk>
Date:	Mon, 20 Aug 2007 23:48:59 +0100
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Segher Boessenkool <segher@...nel.crashing.org>
Cc:	Chris Snook <csnook@...hat.com>,
	Christoph Lameter <clameter@....com>,
	Paul Mackerras <paulus@...ba.org>, heiko.carstens@...ibm.com,
	horms@...ge.net.au, linux-kernel@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, ak@...e.de,
	netdev@...r.kernel.org, cfriesen@...tel.com,
	akpm@...ux-foundation.org, rpjday@...dspring.com,
	Nick Piggin <nickpiggin@...oo.com.au>,
	linux-arch@...r.kernel.org, jesper.juhl@...il.com,
	satyam@...radead.org, zlynx@....org, schwidefsky@...ibm.com,
	Herbert Xu <herbert@...dor.apana.org.au>, davem@...emloft.net,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	wensong@...ux-vs.org, wjiang@...ilience.com
Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures

On Tue, Aug 21, 2007 at 12:04:17AM +0200, Segher Boessenkool wrote:
> And no, RMW on MMIO isn't "problematic" at all, either.
> 
> An RMW op is a read op, a modify op, and a write op, all rolled
> into one opcode.  But three actual operations.

Maybe for some CPUs, but not all.  ARM for instance can't use the
load exclusive and store exclusive instructions to MMIO space.

This means placing atomic_t or bitops into MMIO space is a definite
no-go on ARM.  It breaks.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/