On Wed, Aug 31, 2016 at 11:05 PM, Daniel Vetter <daniel@xxxxxxxx> wrote: > On Wed, Aug 31, 2016 at 10:45 PM, Haixia Shi <hshi@xxxxxxxxxxxx> wrote: >> For details see https://bugs.chromium.org/p/chromium/issues/detail?id=468050 >> >> So drm_mode_config_cleanup() is called from udl_driver_unload() in >> which we found there's still a framebuffer left, hence the WARN in >> drm_crtc.c:5495. This also forcefully releases all the buffers. >> >> A bit later the actual drm_buf_release comes in which attempts to >> release the buffer again. > > Leaving a drm_framebuffer behind on unload is definitely a bug, but > not fixed with this patch here I think. > > The dma-buf lifetime issue is far worse, since we simply don't > handling those leaking past the lifetime of the exporting drm_device > at all. The dma-buf has references to a lot more than just the vma > manager. What we probably need is that every exported dma-buf holds a > ref on the underlying drm_device, but that means untangling the > refcounting&cleanup of that vs unplugging it. Just noticed that these problems started only when dma-buf export support was added (by you) to udl. That dma-buf support is a bit hack-ish (e.g. it leaks sg mappings since udl_unmap_dma_buf isn't implemented. Rough sketch of a fix: - fix up udl_dmabuf.c. We could/should probably put most of these into the core as a set of helpers for drivers which use plain shmem gem objects. - fix udl load/unload to no longer be midlayered, i.e. get rid of the ->load/unload hooks. There's tons of examples and drivers out there for templates. - fix up the unplug hook to correctly unregister everything. With the fixed load/unload all the unplugged tracking is probably no longer neeeded. Also with this you can drop the drm_global_mutex dance from drm_unplug_dev. Also the sequence in drm_unplug_dev is wrong like the midlayered ->unload. First it should do all the unregistering, then release internal resources. Atm it's the other way round. - make sure _all_ public objects (open files, counted by dev->open_count, dma-bufs, ...) hold a full reference onto the drm_device. For the dma-buf case this probably needs changes in drm_prime.c. - Fix that little ordering issue with the leaking fb. It's probably not getting cleanup up as it should in udl_fbdev_unplug. tada, bug fixed for real! Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
