WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] [PATCH] Add RCU support into Xen - Repost

To: "Santos, Jose Renato G" <joserenato.santos@xxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Add RCU support into Xen - Repost
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Tue, 30 Jan 2007 20:23:10 +0000
Cc: "Turner, Yoshio" <yoshio_turner@xxxxxx>, Jose Renato Santos <jsantos@xxxxxxxxxx>, G John Janakiraman <john@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Tue, 30 Jan 2007 12:22:58 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <08CA2245AFCF444DB3AC415E47CC40AF6D46B7@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: Acc5z5YIiS/CKex/Tb+azW+82olglwHqc/i/AMlxYuAAA1KFSg==
Thread-topic: [Xen-devel] [PATCH] Add RCU support into Xen - Repost
User-agent: Microsoft-Entourage/11.3.3.061214
On 30/1/07 7:05 pm, "Santos, Jose Renato G" <joserenato.santos@xxxxxx>
wrote:

>   While doing that I noticed that you removed the definitions of
>   "rcu_read_lock()" and "rcu_read_unlock()" from rcupdate.h.
>   Although they are really NOPs I think it would be good if we use
>   them in all RCU read critical sections, for code clarity
>   and documentation (as linux does).
>   Can we add those back?

This would require some interaction with new find_domain_by_id(). The
invocation of find_domain_by_id() and all subsequent uses of its return
value will need to be contained within an rcu_read_lock()/rcu_read_unlock()
pair which seems kind of a pain. Particularly since this documentation is
weak -- it may not immediately be clear in future what is being protected by
the rcu read-side region (since the lock routines do not take a parameter).
And I'm not sure how the documentation helps: who will it be useful to?

Linux needs them for more than just documentation as it has to disable
preemption (a feature which I don't expect Xen to ever acquire). I don't
know whether it would have them otherwise.

 -- Keir



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel