Re: [PATCH 3/5] drm/debugfs: remove dev->debugfs_list and debugfs_mutex v2

[Christian König <ckoenig.leichtzumerken@xxxxxxxxx>]

Am 12.04.23 um 17:11 schrieb Daniel Vetter:
> On Wed, Apr 12, 2023 at 04:52:04PM +0200, Christian König wrote:
> > The mutex was completely pointless in the first place since any
> > parallel adding of files to this list would result in random
> > behavior since the list is filled and consumed multiple times.
> >
> > Completely drop that approach and just create the files directly but
> > return -ENODEV while opening the file when the minors are not
> > registered yet.
> This part seems to be missing?

I wanted to move this into a separate patch and then forgot to add it. 
Going to fix that.

> The other issue is that partial driver load cleanup now goes boom I think,
> you need to both remove them all in _unregister but also in final drm_dev
> cleanup. Or I'm missing how this works. Maybe you could also use drmm_ for
> that to make sure it's always done.

Good point. Should we call the cleanup function from both the unregister 
and the final drm_dev cleanup or just the later?

Thanks,
Christian.

> There shouldn't be a race as long as the "are we registered yet" check is
> there, since in that case the driver never registered. So no problems
> trying to access the files when they could try to access things which are
> already cleaned up.
>
> I think with those details ironed out this makes some sense to me,
> assuming I understood it correctly.
>
> > v2: rebase on debugfs directory rework, limit access before minors are
> >      registered.
> >
> > Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> > ---
> >   drivers/gpu/drm/drm_debugfs.c     | 27 ++-------------------------
> >   drivers/gpu/drm/drm_drv.c         |  3 ---
> >   drivers/gpu/drm/drm_internal.h    |  5 -----
> >   drivers/gpu/drm/drm_mode_config.c |  2 --
> >   include/drm/drm_device.h          | 15 ---------------
> >   5 files changed, 2 insertions(+), 50 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
> > index 59c3d76d28f4..427c5eb4eca0 100644
> > --- a/drivers/gpu/drm/drm_debugfs.c
> > +++ b/drivers/gpu/drm/drm_debugfs.c
> > @@ -245,7 +245,6 @@ int drm_debugfs_register(struct drm_minor *minor, int minor_id,
> >   			 struct dentry *root)
> >   {
> >   	struct drm_device *dev = minor->dev;
> > -	struct drm_debugfs_entry *entry, *tmp;
> >   	char name[64];
> >   
> >   	INIT_LIST_HEAD(&minor->debugfs_list);
> > @@ -260,30 +259,9 @@ int drm_debugfs_register(struct drm_minor *minor, int minor_id,
> >   	if (dev->driver->debugfs_init && dev->render != minor)
> >   		dev->driver->debugfs_init(minor);
> >   
> > -	list_for_each_entry_safe(entry, tmp, &dev->debugfs_list, list) {
> > -		debugfs_create_file(entry->file.name, 0444,
> > -				    minor->debugfs_root, entry, &drm_debugfs_entry_fops);
> > -		list_del(&entry->list);
> > -	}
> > -
> >   	return 0;
> >   }
> >   
> > -void drm_debugfs_late_register(struct drm_device *dev)
> > -{
> > -	struct drm_minor *minor = dev->primary;
> > -	struct drm_debugfs_entry *entry, *tmp;
> > -
> > -	if (!minor)
> > -		return;
> > -
> > -	list_for_each_entry_safe(entry, tmp, &dev->debugfs_list, list) {
> > -		debugfs_create_file(entry->file.name, 0444,
> > -				    minor->debugfs_root, entry, &drm_debugfs_entry_fops);
> > -		list_del(&entry->list);
> > -	}
> > -}
> > -
> >   int drm_debugfs_remove_files(const struct drm_info_list *files, int count,
> >   			     struct drm_minor *minor)
> >   {
> > @@ -353,9 +331,8 @@ void drm_debugfs_add_file(struct drm_device *dev, const char *name,
> >   	entry->file.data = data;
> >   	entry->dev = dev;
> >   
> > -	mutex_lock(&dev->debugfs_mutex);
> > -	list_add(&entry->list, &dev->debugfs_list);
> > -	mutex_unlock(&dev->debugfs_mutex);
> > +	debugfs_create_file(name, 0444, dev->debugfs_root, entry,
> > +			    &drm_debugfs_entry_fops);
> >   }
> >   EXPORT_SYMBOL(drm_debugfs_add_file);
> >   
> > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> > index 05b831f9fe71..f928b4490ece 100644
> > --- a/drivers/gpu/drm/drm_drv.c
> > +++ b/drivers/gpu/drm/drm_drv.c
> > @@ -597,7 +597,6 @@ static void drm_dev_init_release(struct drm_device *dev, void *res)
> >   	mutex_destroy(&dev->clientlist_mutex);
> >   	mutex_destroy(&dev->filelist_mutex);
> >   	mutex_destroy(&dev->struct_mutex);
> > -	mutex_destroy(&dev->debugfs_mutex);
> >   	drm_legacy_destroy_members(dev);
> >   }
> >   
> > @@ -638,14 +637,12 @@ static int drm_dev_init(struct drm_device *dev,
> >   	INIT_LIST_HEAD(&dev->filelist_internal);
> >   	INIT_LIST_HEAD(&dev->clientlist);
> >   	INIT_LIST_HEAD(&dev->vblank_event_list);
> > -	INIT_LIST_HEAD(&dev->debugfs_list);
> >   
> >   	spin_lock_init(&dev->event_lock);
> >   	mutex_init(&dev->struct_mutex);
> >   	mutex_init(&dev->filelist_mutex);
> >   	mutex_init(&dev->clientlist_mutex);
> >   	mutex_init(&dev->master_mutex);
> > -	mutex_init(&dev->debugfs_mutex);
> >   
> >   	ret = drmm_add_action_or_reset(dev, drm_dev_init_release, NULL);
> >   	if (ret)
> > diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
> > index 5c6e1cadf09b..c5fadbd3fd7d 100644
> > --- a/drivers/gpu/drm/drm_internal.h
> > +++ b/drivers/gpu/drm/drm_internal.h
> > @@ -185,7 +185,6 @@ void drm_debugfs_dev_register(struct drm_device *dev);
> >   int drm_debugfs_register(struct drm_minor *minor, int minor_id,
> >   			 struct dentry *root);
> >   void drm_debugfs_cleanup(struct drm_minor *minor);
> > -void drm_debugfs_late_register(struct drm_device *dev);
> >   void drm_debugfs_connector_add(struct drm_connector *connector);
> >   void drm_debugfs_connector_remove(struct drm_connector *connector);
> >   void drm_debugfs_crtc_add(struct drm_crtc *crtc);
> > @@ -206,10 +205,6 @@ static inline void drm_debugfs_cleanup(struct drm_minor *minor)
> >   {
> >   }
> >   
> > -static inline void drm_debugfs_late_register(struct drm_device *dev)
> > -{
> > -}
> > -
> >   static inline void drm_debugfs_connector_add(struct drm_connector *connector)
> >   {
> >   }
> > diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> > index 87eb591fe9b5..8525ef851540 100644
> > --- a/drivers/gpu/drm/drm_mode_config.c
> > +++ b/drivers/gpu/drm/drm_mode_config.c
> > @@ -54,8 +54,6 @@ int drm_modeset_register_all(struct drm_device *dev)
> >   	if (ret)
> >   		goto err_connector;
> >   
> > -	drm_debugfs_late_register(dev);
> > -
> >   	return 0;
> >   
> >   err_connector:
> > diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
> > index 3cf12b14232d..c490977ee250 100644
> > --- a/include/drm/drm_device.h
> > +++ b/include/drm/drm_device.h
> > @@ -318,21 +318,6 @@ struct drm_device {
> >   	 */
> >   	struct dentry *debugfs_root;
> >   
> > -	/**
> > -	 * @debugfs_mutex:
> > -	 *
> > -	 * Protects &debugfs_list access.
> > -	 */
> > -	struct mutex debugfs_mutex;
> > -
> > -	/**
> > -	 * @debugfs_list:
> > -	 *
> > -	 * List of debugfs files to be created by the DRM device. The files
> > -	 * must be added during drm_dev_register().
> > -	 */
> > -	struct list_head debugfs_list;
> > -
> >   	/* Everything below here is for legacy driver, never use! */
> >   	/* private: */
> >   #if IS_ENABLED(CONFIG_DRM_LEGACY)
> > --
> > 2.34.1