Re: [PATCH] drm/gem: modernize locks to use scoped_guard()

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Mon, Jun 22, 2026 at 06:22:27PM +0530, biren pandya wrote:
> On Mon, Jun 22, 2026 at 5:25 PM Laurent Pinchart wrote:
> > On Tue, Jun 16, 2026 at 11:49:57PM +0530, Biren Pandya wrote:
> > > Several GEM core functions manually managed mutex_lock() and
> > > mutex_unlock() over single scopes or error paths. This adds boilerplate
> > > and carries the risk of lock leaks if error paths are refactored.
> > >
> > > Modernize these locks by deploying the <linux/cleanup.h> scoped_guard()
> > > macro. This ensures that the locks are reliably dropped when the block
> > > exits, cleanly removing goto out_unlock paths and tightening the
> > > lifecycle.
> >
> > What's the reason for doing so in in drm_gem and not other areas in DRM
> > ?
> 
> Hi Laurent,
> 
> Thanks for taking a look.
> No deeper reason than it being where I happened to start — I didn't
> mean to single it out, and I'd rather the treatment be consistent than
> piecemeal.
> 
> > > @@ -1021,37 +1018,34 @@ int drm_gem_change_handle_ioctl(struct drm_device *dev, void *data,
> > >               goto out;
> > >       }
> > >
> > > -     mutex_lock(&file_priv->prime.lock);
> > > +     scoped_guard(mutex, &file_priv->prime.lock) {
> > > +             spin_lock(&file_priv->table_lock);
> > > +             ret = idr_alloc(&file_priv->object_idr, obj, handle, handle + 1,
> > > +                             GFP_NOWAIT);
> > > +             spin_unlock(&file_priv->table_lock);
> >
> > And why don't you use guards for the spinlock as well ?
> 
> Fair point — the spinlocks here are equally good candidates; I only
> kept v1 to mutexes to keep it small.
> 
> That said, this is a pure cleanup with no functional change, so it's
> entirely your call whether it's worth carrying.
> If you'd like it, I'll send a v2 that converts both the mutexes and
> the spinlocks in drm_gem.c consistently. If you'd prefer not to take
> cleanup-only churn, I'm happy to drop it — no problem either way.

I'll let the maintainers of that code decide (I'm not one of them).

-- 
Regards,

Laurent Pinchart