[Intel-gfx] [RFC][PATCH 11/11] drm: Sprinkle lockdep asserts for edid/display_info

[Ville Syrjälä]

On Tue, Mar 06, 2018 at 10:31:27AM +0100, Daniel Vetter wrote:
> On Tue, Feb 27, 2018 at 02:57:00PM +0200, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > edid and display_info are protected by mode_config.mutex. Add lockdep
> > asserts to make sure we're not accessing things w/o the lock.
> > 
> > FIXME: pretty sure this will blow up with amdgpu as they seem
> > to be doing edid updates even from the modeset path. Need to figure
> > out what to do about that. Maybe protect the edid/display info with
> > with connection_mutex instead of mode_config.mutex?
> 
> Imo not doing EDID udpates from the modeset path is the right fix. I can't
> think of any reasonable reason to do that at least. Can you point me at
> the relevant amdgpu code pls (I'm lazy, sry)?

It was some MST thing I believe... (should have written it down)

amdgpu_dm_atomic_check() -> dm_update_crtcs_state() ->
create_stream_for_sink() -> dm_dp_mst_dc_sink_create() ->
get_edid/update_edid_property

> 
> Otherwise I think this is a real good patch.
> 
> Thanks, Daniel
> 
> > 
> > Cc: Keith Packard <keithp at keithp.com>
> > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> > Cc: Harry Wentland <harry.wentland at amd.com>
> > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/drm_connector.c    | 4 ++++
> >  drivers/gpu/drm/drm_edid.c         | 2 ++
> >  drivers/gpu/drm/drm_probe_helper.c | 2 +-
> >  3 files changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > index 122060792b6f..a9f3536f4e94 100644
> > --- a/drivers/gpu/drm/drm_connector.c
> > +++ b/drivers/gpu/drm/drm_connector.c
> > @@ -1374,6 +1374,8 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector,
> >  	size_t size = 0;
> >  	int ret;
> >  
> > +	lockdep_assert_held(&dev->mode_config.mutex);
> > +
> >  	/* ignore requests to set edid when overridden */
> >  	if (connector->override_edid)
> >  		return 0;
> > @@ -1770,6 +1772,8 @@ void drm_connector_reset_display_info(struct drm_connector *connector)
> >  {
> >  	struct drm_display_info *info = &connector->display_info;
> >  
> > +	lockdep_assert_held(&connector->dev->mode_config.mutex);
> > +
> >  	memset(info, 0, sizeof(*info));
> >  }
> >  EXPORT_SYMBOL_GPL(drm_connector_reset_display_info);
> > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> > index 618093c4a039..7f9e9236114b 100644
> > --- a/drivers/gpu/drm/drm_edid.c
> > +++ b/drivers/gpu/drm/drm_edid.c
> > @@ -4440,6 +4440,8 @@ u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edi
> >  	struct drm_display_info *info = &connector->display_info;
> >  	u32 quirks = edid_get_quirks(edid);
> >  
> > +	lockdep_assert_held(&connector->dev->mode_config.mutex);
> > +
> >  	info->width_mm = edid->width_cm * 10;
> >  	info->height_mm = edid->height_cm * 10;
> >  
> > diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> > index 7dc7e635d7e4..2a2afcf72788 100644
> > --- a/drivers/gpu/drm/drm_probe_helper.c
> > +++ b/drivers/gpu/drm/drm_probe_helper.c
> > @@ -400,7 +400,7 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
> >  	enum drm_connector_status old_status;
> >  	struct drm_modeset_acquire_ctx ctx;
> >  
> > -	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
> > +	lockdep_assert_held(&dev->mode_config.mutex);
> >  
> >  	drm_modeset_acquire_init(&ctx, 0);
> >  
> > -- 
> > 2.13.6
> > 
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Ville Syrjälä
Intel OTC