[libvirt] [PATCH] Avoid invoking the qemu monitor destroy callback if the constructor fails

[Daniel P. Berrange]

On Wed, Jun 30, 2010 at 02:40:58PM +0200, Jiri Denemark wrote:
> > diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
> > index f428665..ff613a0 100644
> > --- a/src/qemu/qemu_monitor.c
> > +++ b/src/qemu/qemu_monitor.c
> > @@ -671,6 +671,12 @@ qemuMonitorOpen(virDomainObjPtr vm,
> >      return mon;
> >  
> >  cleanup:
> > +    /* We don't want the 'destroy' callback invoked during
> > +     * cleanup from construction failure, because that can
> > +     * give a double-unref on virDomainObjPtr in the caller,
> > +     * so kill the callbacks now.
> > +     */
> > +    mon->cb = NULL;
> >      qemuMonitorUnlock(mon);
> >      qemuMonitorClose(mon);
> >      return NULL;
> 
> Unfortunately, this patch causes segfaults since qemuMonitorFree is not ready
> to see mon->cb == NULL. On the other hand, we are lucky that this patch didn't
> make it into the repository yet, so we can squash the following patch into it
> before pushing:

ACK, I've included this in the patch & pushed the result

> 
> diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
> index f428665..9b050a0 100644
> --- a/src/qemu/qemu_monitor.c
> +++ b/src/qemu/qemu_monitor.c
> @@ -198,7 +198,7 @@ void qemuMonitorUnlock(qemuMonitorPtr mon)
>  static void qemuMonitorFree(qemuMonitorPtr mon)
>  {
>      VIR_DEBUG("mon=%p", mon);
> -    if (mon->cb->destroy)
> +    if (mon->cb && mon->cb->destroy)
>          (mon->cb->destroy)(mon, mon->vm);
>      if (virCondDestroy(&mon->notify) < 0)
>      {}


Daniel
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