Re: [Xen-devel] [PATCH v4 21/23] xen/vpl011: buffer out chars when the backend is xen

[Julien Grall <julien.grall@xxxxxxx>]

Hi Stefano,

On 10/20/18 12:20 AM, Stefano Stabellini wrote:
> On Mon, 8 Oct 2018, Jan Beulich wrote:
> > > > > On 05.10.18 at 20:47, <sstabellini@xxxxxxxxxx> wrote:
> > > --- a/xen/drivers/char/console.c
> > > +++ b/xen/drivers/char/console.c
> > > @@ -406,6 +406,13 @@ static void dump_console_ring_key(unsigned char key)
> > >    */
> > >   static unsigned int __read_mostly console_rx = 0;
> > >   
> > > +struct domain *console_input_domain(void)
> > > +{
> > > +    if ( console_rx == 0 )
> > > +            return NULL;
> > > +    return get_domain_by_id(console_rx - 1);
> > This acquires a domain reference, yet I can't see that reference
> > getting dropped anywhere in the caller.
> Well spotted!
>
> I'll add a comment here as a reminder, and I'll drop the domain
> reference in the caller (xen/arch/arm/vpl011.c:vpl011_write_data_xen).
Why do you use get_domain_by_id() and not rcu_lock_domain_by_id()? The 
latter is recommend for short live reference.
Cheers,

--
Julien Grall

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