linux-kernel - Re: [PATCH 0/5] x86-32: improve atomic64

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Message-ID: <20100301084923.GG26848@brick.ozlabs.ibm.com>
Date:	Mon, 1 Mar 2010 19:49:23 +1100
From:	Paul Mackerras <paulus@...ba.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Luca Barbieri <luca@...a-barbieri.com>,
	Ingo Molnar <mingo@...e.hu>, a.p.zijlstra@...llo.nl,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] x86-32: improve atomic64_t functions (v2)

On Sun, Feb 28, 2010 at 11:35:31PM -0800, H. Peter Anvin wrote:

> On 02/26/2010 03:23 AM, Luca Barbieri wrote:
> > Sent patches, both to conditionally perform the test and implement the
> > functions for x86 and x86-64.
> 
> Yes, and with the test turned on, the kernel crashes immediately on boot
> on x86-64.
> 
> Some minor investigation reveals the following:
> 
> lib/atomic64.c has the wrong return value for atomic64_add_unless().
> With "wrong" I mean it is the opposite sense compared to
> atomic_add_unless(), not just on x86 but on all architectures.
> 
> Accordingly, I have to conclude that lib/atomic64.c is buggy, and that
> since your test matches that bug, I will have to conclude that your
> x86-32 implementation is also buggy.  Thus, please send patches to fix
> your test and your 32-bit implementations (and preferrably
> lib/atomic64.c too, but I can do that just fine.)
> 
> Cc: Paul Mackerras who did the generic atomic64_t implementation for
> verification that this is indeed a bug.

Yes, it sure looks like it.  *blush*

Paul.
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