[PATCH v7 05/28] dma-heap: Add proper kref handling on dma-buf heaps

[John Stultz]

On Sat, Jul 20, 2024 at 8:13 AM Markus Elfring <Markus.Elfring at web.de> wrote:
>
> …
> > +++ b/drivers/dma-buf/dma-heap.c
> …
> > +static void dma_heap_release(struct kref *ref)
> > +{
> …
> > +     mutex_lock(&heap_list_lock);
> > +     list_del(&heap->list);
> > +     mutex_unlock(&heap_list_lock);
> …
>
> Under which circumstances would you become interested to apply a statement
> like “guard(mutex)(&heap_list_lock);”?
> https://elixir.bootlin.com/linux/v6.10/source/include/linux/mutex.h#L196

This strikes me as a strange place to apply it, as it seems like it
would grow the lock hold time to the entire scope of the function
unless one created a subscope for just the list_del, at which point
you're not saving much or really improving readability.  I definitely
think guard usage is very interesting in places where locks are
released in multiple exit paths, etc. but this is a very trivial and
straightforward lock/unlock usage, so I fret I don't quite understand
the suggestion.

thanks
-john