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: spinlock requests (was RE: [Xen-devel] [Patch] don't spin with irq d

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxxxx>, Juergen Gross <juergen.gross@xxxxxxxxxxxxxxxxxxx>
Subject: Re: spinlock requests (was RE: [Xen-devel] [Patch] don't spin with irq disabled)
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Fri, 03 Apr 2009 08:17:24 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Fri, 03 Apr 2009 00:18:15 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <d26aa59f-57f6-4542-827b-6dfe0c15e422@default>
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: Acmz6Cuasc0ME0d5QwaiAQfAQme0+gARBCyS
Thread-topic: spinlock requests (was RE: [Xen-devel] [Patch] don't spin with irq disabled)
User-agent: Microsoft-Entourage/12.15.0.081119
On 03/04/2009 00:08, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

>> Well the race is still impossible afaics. Unless your
>> _raw_rw_is_write_locked() was checking for ==0 rather than
>> <=0.
> 
> Finally got a chance to go back and reproduce and figure
> this one out.  The crash is still occurring.  My code
> definitely checks for <=0.  BUT the declaration of
> raw_rwlock_t declares the lock as "volatile UNSIGNED int",
> so the compiler blithely generates a check for == 0.
> 
> Can I assume the fix is to change the declaration to
> int instead of unsigned int, or will that cause problems
> elsewhere?

Oh dear. Yes, that's the fix!

 -- Keir



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

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