On Thu, Feb 16, 2023 at 12:33:08PM +0100, Daniel Vetter wrote:
> On Thu, Feb 09, 2023 at 09:18:38AM +0100, 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.
> >
> > This also re-adds the debugfs files to the render node directory and
> > removes drm_debugfs_late_register().
> >
> > Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> > ---
> > drivers/gpu/drm/drm_debugfs.c | 32 +++++++------------------------
> > 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, 7 insertions(+), 50 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
> > index 558e3a7271a5..a40288e67264 100644
> > --- a/drivers/gpu/drm/drm_debugfs.c
> > +++ b/drivers/gpu/drm/drm_debugfs.c
> > @@ -246,31 +246,9 @@ void drm_debugfs_dev_register(struct drm_device *dev)
> > void drm_debugfs_minor_register(struct drm_minor *minor)
> > {
> > struct drm_device *dev = minor->dev;
> > - struct drm_debugfs_entry *entry, *tmp;
> >
> > if (dev->driver->debugfs_init)
> > 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);
> > - }
> > -}
> > -
> > -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,
> > @@ -343,9 +321,13 @@ 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->primary->debugfs_root, entry,
> > + &drm_debugfs_entry_fops);
> > +
> > + /* TODO: This should probably only be a symlink */
> > + if (dev->render)
> > + debugfs_create_file(name, 0444, dev->render->debugfs_root,
> > + entry, &drm_debugfs_entry_fops);
>
> Nope. You are fundamentally missing the point of all this, which is:
>
> - drivers create debugfs files whenever they want to, as long as it's
> _before_ drm_dev_register is called.
>
> - drm_dev_register will set them all up.
>
> This is necessary because otherwise you have the potential for some nice
> oops and stuff when userspace tries to access these files before the
> driver is ready.
>
> Note that with sysfs all this infrastructure already exists, which is why
> you can create sysfs files whenever you feel like, and things wont go
> boom.
>
> So yeah we need the list.
>
> This also means that we really should not create the debugfs directories
> _before_ drm_dev_register is called. That's just fundamentally not how
> device interface setup should work:
>
> 1. you allocate stucts and stuff
> 2. you fully init everything
> 3. you register interfaces so they become userspace visible
What I forgot to add: The mutex seems surplus and could probably be
removed. But we need the mutex once this infra is extracted to other drm
things like connector/crtc debugfs files, because you can hotplug
connectors. But maybe the mutex isn't even need in that case (since for a
single object you still should not multi-thread anything).
So removing the mutex here seems like a reasonable thing to do, but
funamentally the list and the entire delayed debugfs setup must stay.
Otherwise we cannot remove the entire debugfs_init midlayer mess without
creating huge amounts of driver bugs in the init sequencing.
-Daniel
> -Daniel
>
> > }
> > EXPORT_SYMBOL(drm_debugfs_add_file);
> >
> > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> > index 2cbe028e548c..e7b88b65866c 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 5ff7bf88f162..e215d00ba65c 100644
> > --- a/drivers/gpu/drm/drm_internal.h
> > +++ b/drivers/gpu/drm/drm_internal.h
> > @@ -188,7 +188,6 @@ int drm_debugfs_init(struct drm_minor *minor, int minor_id,
> > void drm_debugfs_dev_register(struct drm_device *dev);
> > void drm_debugfs_minor_register(struct drm_minor *minor);
> > 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);
> > @@ -205,10 +204,6 @@ 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 7cf4afae2e79..900ad7478dd8 100644
> > --- a/include/drm/drm_device.h
> > +++ b/include/drm/drm_device.h
> > @@ -311,21 +311,6 @@ struct drm_device {
> > */
> > struct drm_fb_helper *fb_helper;
> >
> > - /**
> > - * @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
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
