From: Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: [PATCH] fix pgd_lock deadlock
Date: Tue, 22 Feb 2011 09:08:54 -0800
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To: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Xen-devel@lists.xensource.com" <Xen-devel@lists.xensource.com>, Ian Campbell <Ian.Campbell@citrix.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Larry Woodman <lwoodman@redhat.com>, the arch/x86 maintainers <x86@kernel.org>, Hugh Dickins <hughd@google.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Jan Beulich <JBeulich@novell.com>, Johannes Weiner <jweiner@redhat.com>, Andi Kleen <andi@firstfloor.org>, "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>, Andrew Morton <akpm@linux-foundation.org>
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On 02/22/2011 06:34 AM, Andrea Arcangeli wrote:
> On Tue, Feb 22, 2011 at 02:22:53PM +0000, Jan Beulich wrote:
>> If everyone's okay with putting a couple of "if (xen_pv_domain())"
>> into mm/fault.c - sure. I would have thought that this wouldn't be
>> liked, hence the suggestion to make this depend on seeing the
>> backlink be non-NULL.
> I prefer the if (xen_pv_domain) so it also gets optimized away
> at build time when CONFIG_XEN=n. I think it's also more self
> explanatory to read.

Eh, very not keen about that.  I'd only consider it as a last resort.

In practice CONFIG_XEN is always enabled in distros, so the conditional
would always be done at runtime.

    J