Re: [PATCH v7 45/49] media: core: Add bitmap manage bufs array entries

[Benjamin Gaignard]

Le 20/09/2023 à 16:56, Hans Verkuil a écrit :
> On 20/09/2023 16:30, Benjamin Gaignard wrote:
> <snip>
>
> > > >        num_buffers = min_t(unsigned int, num_buffers,
> > > >                    q->max_allowed_buffers - vb2_get_num_buffers(q));
> > > >    -    first_index = vb2_get_num_buffers(q);
> > > > +    first_index = bitmap_find_next_zero_area(q->bufs_map, q->max_allowed_buffers,
> > > > +                         0, num_buffers, 0);
> > > >          if (first_index >= q->max_allowed_buffers)
> > > >            return 0;
> > > > @@ -675,7 +678,13 @@ static void __vb2_queue_free(struct vb2_queue *q, unsigned int buffers)
> > > >      struct vb2_buffer *vb2_get_buffer(struct vb2_queue *q, unsigned int index)
> > > >    {
> > > > -    if (index < q->num_buffers)
> > > > +    if (!q->bufs_map || !q->bufs)
> > > > +        return NULL;
> > > I don't think this can ever happen.
> > I got kernel crash without them.
> > I will keep them.
> What is the backtrace? How can this happen? It feels wrong that this can be
> called with a vb2_queue that apparently is not properly initialized.

I will add backtrace when doing test on v8

> > > > +
> > > > +    return (bitmap_weight(q->bufs_map, q->max_allowed_buffers) > 0);
> > > How about:
> > >
> > >      return vb2_get_num_buffers(q) > 0;
> > vb2_get_num_buffers is defined in videobuf2-core.c, I'm not sure that
> > an inline function could depend of a module function.
> Not a problem. E.g. v4l2-ctrls.h is full of such static inlines.

I will change vb2_get_num_buffers() to inline function that solve the problem too.

> Regards,
>
> 	Hans