On Wed, Jun 15, 2016 at 12:48:23PM +0100, Chris Wilson wrote:
> On Tue, Jun 14, 2016 at 08:51:02PM +0200, Daniel Vetter wrote:
> > Another place gone where modern drivers could have hit
> > dev->struct_mutex.
> >
> > To avoid too deeply nesting control flow rework it a bit.
> >
> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/drm_auth.c | 20 ++++++++++++--------
> > 1 file changed, 12 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c
> > index e015a7edb154..a58b2eb0d004 100644
> > --- a/drivers/gpu/drm/drm_auth.c
> > +++ b/drivers/gpu/drm/drm_auth.c
> > @@ -246,11 +246,14 @@ int drm_master_open(struct drm_file *file_priv)
> > void drm_master_release(struct drm_file *file_priv)
> > {
> > struct drm_device *dev = file_priv->minor->dev;
> > + struct drm_master *master = file_priv->master;
> > +
>
> Spare newline.
>
> > mutex_lock(&dev->master_mutex);
> > - if (file_priv->is_master) {
> > - struct drm_master *master = file_priv->master;
> > + if (!file_priv->is_master)
> > + goto out_unlock;
> >
> > + if (!drm_core_check_feature(dev, DRIVER_MODESET)) {
> > /*
> > * Since the master is disappearing, so is the
> > * possibility to lock.
> > @@ -264,19 +267,20 @@ void drm_master_release(struct drm_file *file_priv)
> > wake_up_interruptible_all(&master->lock.lock_queue);
> > }
> > mutex_unlock(&dev->struct_mutex);
> > + }
> >
> > - if (file_priv->minor->master == file_priv->master) {
> > - /* drop the reference held my the minor */
> > - if (dev->driver->master_drop)
> > - dev->driver->master_drop(dev, file_priv, true);
> > - drm_master_put(&file_priv->minor->master);
> > - }
> > + if (file_priv->minor->master == file_priv->master) {
> > + /* drop the reference held my the minor */
> > + if (dev->driver->master_drop)
> > + dev->driver->master_drop(dev, file_priv, true);
> > + drm_master_put(&file_priv->minor->master);
> > }
> >
> > /* drop the master reference held by the file priv */
> > if (file_priv->master)
> > drm_master_put(&file_priv->master);
> > file_priv->is_master = 0;
> > +out_unlock:
>
> This changes the reference counting, and from my quick scan we can have
> a reference on file_priv->master but file_priv->is_master == 0.
Indeed, I've created a leak. Will fix.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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