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] RCU locks in Xen!

To: "Jayaraman, Bhaskar" <Bhaskar.Jayaraman@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] RCU locks in Xen!
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 24 Feb 2009 04:05:38 -0800
Cc:
Delivery-date: Tue, 24 Feb 2009 04:06:09 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <F4789BF54654AC44982AC0ED2DE2E64B2CC5E75A77@xxxxxxxxxxxxxxxxx>
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/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AcmWbhkp2j2qBLAQRWucsTuSkW0vygACht7x
Thread-topic: [Xen-devel] RCU locks in Xen!
User-agent: Microsoft-Entourage/12.15.0.081119
complete_domain_destroy() is called via call_rcu().

 -- Keir

On 24/02/2009 02:53, "Jayaraman, Bhaskar" <Bhaskar.Jayaraman@xxxxxxx> wrote:

> I see that rcu locks in Xen code are empty or in other words do nothing, and
> even rcu_dereference also doesn¹t assign pointers through a temporary
> variable. So is it possible that while domain destruction, while I¹m
> traversing through the domain_hash, list as in rcu_lock_domain_by_id(), I
> could end up with an invalid pointer?
> This is because I see that domain_destroy simply calls complete_domain_destroy
> which frees up the domain pointer and it seems like it could be possible that
> while traversing through the hash list in rcu_lock_domain_by_id I could end up
> with a domain pointer which domain_destroy might have just destroyed and I
> can¹t proceed further down the list.
>  
> Please let me know if there¹s something else that I¹m overlooking and if not
> then how come we don¹t see domains/Xen crashing because of this caveat.
>  
> Regards,
> Bhaskar.
> 



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

<Prev in Thread] Current Thread [Next in Thread>