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From: Roman Zippel <zippel@linux-m68k.org>
To: Luca Barbieri <ldb@ldb.ods.org>
Cc: Linux-Kernel ML <linux-kernel@vger.kernel.org>,
	Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [PATCH] [2.5] asm-generic/atomic.h and changes to arm, parisc, mips, m68k, sh, cris to use it
Date: Fri, 9 Aug 2002 01:04:40 +0200 (CEST)	[thread overview]
Message-ID: <Pine.LNX.4.44.0208090100100.8911-100000@serv> (raw)
In-Reply-To: <1028846417.1669.95.camel@ldb>

Hi,

On 9 Aug 2002, Luca Barbieri wrote:

> > The compiler can cache the value in a register
> It shouldn't since it is volatile and the machine has instructions with
> memory operands.

volatile is no guarantee for that:

volatile int x;

void f(int y)
{
        x += y;
}

becomes:

	move.l x,%d0
	add.l 8(%a6),%d0
	move.l %d0,x

I agree that volatile should avoid caching, but it does not guarantee an
atomic modify.

bye, Roman


  reply	other threads:[~2002-08-08 23:02 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-08-08 21:43 Luca Barbieri
2002-08-08 21:58 ` Roman Zippel
2002-08-08 22:11   ` Luca Barbieri
2002-08-08 22:27     ` Roman Zippel
2002-08-08 22:40       ` Luca Barbieri
2002-08-08 23:04         ` Roman Zippel [this message]
2002-08-09  0:11         ` Alan Cox
2002-08-08 23:09           ` Luca Barbieri
2002-08-09  3:52           ` H. Peter Anvin
2002-08-08 23:45     ` Alan Cox
2002-08-12 11:16     ` David Woodhouse
2002-08-12 12:03       ` Luca Barbieri
2002-08-08 23:29 ` Russell King
2002-08-09  0:41   ` [PATCH] [2.5] (v2) " Luca Barbieri

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