Re: [Qemu-devel] [PATCH] Fix hanging user monitor when using balloon command

[Luiz Capitulino <lcapitulino@redhat.com>]

On Mon, 22 Feb 2010 10:51:20 -0600
Adam Litke <agl@us.ibm.com> wrote:

> On Fri, 2010-02-19 at 15:47 -0600, Anthony Liguori wrote:
> > On 02/12/2010 02:55 PM, Adam Litke wrote:
> > > Arghh... Adding missing S-O-B
> > >
> > > Hi Anthony.  I wonder if there was a problem when importing my async
> > > command handler patchset.  Since the 'balloon' command completes
> > > immediately, it must call the completion callback before returning.
> > > That call was missing but is added by the patch below.
> > >
> > > Signed-off-by: Adam Litke<agl@us.ibm.com>
> > >    
> > 
> > Applied.  Thanks.
> 
> This patch application failed.  My patch adds a cb() call in
> do_balloon(), but the change in git has added the cb() call to
> do_info_balloon().  That is causing qemu segfaults.  Applying the
> following should correct the damage.  Thanks.
> 
> Fix for commit: 5c366a8a3d7ac71beda8499caa815cb3ea95eb58
> 
> The cb() call is needed in do_balloon(), not do_info_balloon().

 It won't segfault on QMP, but will print a duplicated response on
query-balloon and no success response on balloon.

 This patch fixes both. One question, though:

> @@ -2332,6 +2331,7 @@ static int do_balloon(Monitor *mon, const QDict *params,
>          return -1;
>      }
>  
> +    cb(opaque, NULL);
>      return 0;
>  }

 Can't (or shouldn't) this be called by common code upon handler
completion?