From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir@xensource.com>
Subject: Re: Fwd: Re: struct page field arrangement
Date: Fri, 16 Mar 2007 14:13:13 +0000
Message-ID: <C2205679.BAA4%keir@xensource.com>
References: <45FAADF9.76E4.0078.0@novell.com>
Mime-Version: 1.0
Content-Type: text/plain;
	charset="US-ASCII"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xensource.com>
In-Reply-To: <45FAADF9.76E4.0078.0@novell.com>
List-Unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xensource.com>
List-Help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-Subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
Sender: xen-devel-bounces@lists.xensource.com
Errors-To: xen-devel-bounces@lists.xensource.com
To: Jan Beulich <jbeulich@novell.com>, Keir Fraser <keir@xensource.com>
Cc: xen-devel@lists.xensource.com
List-Id: xen-devel@lists.xenproject.org

On 16/3/07 13:47, "Jan Beulich" <jbeulich@novell.com> wrote:

> Btw., another question that made me wonder already when doing the
> original patch: why is it that x86-64 properly uses locking for mm_pin_all(),
> yet i386 doesn't need to?

Neither needs to. Well, assuming you're not using CONFIG_PREEMPT. :-)

Either we are in stop_machine context, or we have offlined all other CPUs
via cpu hotplug. In the absence of involuntary preemption it's therefore
safe to proceed without locking. But probably inadvisable (we'd like to
support full CONFIG_PREEMPT sometime in the future)... I think the 386 code
should be changed to match x86/64.

 -- Keir