On Wed, Aug 19, 2020 at 03:46:30PM +0200, Cezary Rojewski wrote:
> On 2020-08-18 1:50 PM, Andy Shevchenko wrote:
> > On Mon, Aug 17, 2020 at 01:12:01PM +0200, Cezary Rojewski wrote:
> > > On 2020-08-13 8:51 PM, Andy Shevchenko wrote:
> > > > On Wed, Aug 12, 2020 at 10:57:42PM +0200, Cezary Rojewski wrote:
...
> > > > > + bool lp;
> > > > > +
> > > > > + if (list_empty(&cdev->stream_list))
> > > > > + return catpt_dsp_select_lpclock(cdev, true, true);
> > > > > +
> > > > > + lp = true;
> > > > > + list_for_each_entry(stream, &cdev->stream_list, node) {
> > > > > + if (stream->prepared) {
> > > > > + lp = false;
> > > > > + break;
> > > > > + }
> > > > > + }
> > > > > +
> > > > > + return catpt_dsp_select_lpclock(cdev, lp, true);
> > > >
> > > > Seems too much duplication.
> > > >
> > > > struct catpt_stream_runtime *stream;
> > > >
> > > > list_for_each_entry(stream, &cdev->stream_list, node) {
> > > > if (stream->prepared)
> > > > return catpt_dsp_select_lpclock(cdev, false, true);
> > > > }
> > > >
> > > > return catpt_dsp_select_lpclock(cdev, true, true);
> > > >
> > > >
> > > > Better?
> > >
> > > list_first_entry (part of list_for_each_entry) expects list to be non-empty.
> > > ->streal_list may be empty when invoking catpt_dsp_update_lpclock().
> >
> > I didn't get this. Can you point out where is exactly problematic place?
> >
>
> list_for_each_entry makes use of list_first_entry when initializing 'pos'
> index variable.
Correct.
> Documentation for list_first_entry reads: "Note, that list
> is expected to be not empty"
Correct.
> so I'm validating list's status before moving
> on to the loop as stream_list may be empty when catpt_dsp_update_lpclock()
> gets called.
But here you missed the second part of the for-loop, i.e. exit conditional.
If your assumption (that list_for_each_*() is not empty-safe) is correct,
it would be disaster in global kernel source level.
--
With Best Regards,
Andy Shevchenko
