On Thu, Apr 10, 2014 at 02:47:52PM +0300, Tomi Valkeinen wrote: > Hi, > > I've been debugging omapdrm issues on top of the latest drm mainline > changes. Sometimes a drm_framebuffer ref count drops to -1 when aborting > a drm application, or unloading the modules. > > The setup is very basic, just a single crtc with the crtc's primary plane. > > What seems to happen is: > > - App is started > > - fb is created, and taken into use by omapdrm. omapdrm takes a ref to > the fb. > > - the app is starts to shut down > > - drm_framebuffer_remove is called > > - fb->refcount.refcount > 1, so it goes to disable stuff > > - drm_plane_force_disable is called for the primary plane > > - drm_plane_force_disable does plane->disable_plane, which on omapdrm > puts stuff on a workqueue as plane cannot be disabled immediately > > - drm_plane_force_disable calls __drm_framebuffer_unreference() > > - at the end of drm_framebuffer_remove(), there's > drm_framebuffer_unreference, which causes ref count to go to zero, and > the fb to be destroyed > > - a bit later, the queued work is ran, which does > drm_framebuffer_unreference(), and ref count goes to -1. Here omapdrm is > removing the ref that had been taken in the beginning. > > > So the explicit unref done by drm_plane_force_disable() seems a bit out > of place. I can't figure out which drm_framebuffer_reference() would be > the matching one for the unref done by drm_plane_force_disable(). > > Any ideas what ref is that? Or is the __drm_framebuffer_unreference() > extra in drm_plane_force_disable()? plane->fb is holding a reference which should have been acquired in drm_mode_setplane. It's not really explicit since drm_framebuffer_lookup implicitly grabs a ref for you. Hence when we disable the plane and set plane->fb = NULL we must drop that ref again. So that's not the bug, but clearly something goes wrong somewhere. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
