On Thu, Sep 1, 2016 at 3:22 AM, Haixia Shi <hshi at chromium.org> wrote: > Daniel > > Thanks! I agree the PATCH 1/2 needs some more work. > > What do you think about the PATCH 2/2 (suspend/resume) -- would it > make sense to review it as a single standalone patch?
Sure, but I have no clue about usb or udl-specific issues (I only analyzed the generic lifetime issues in patch 1/2), I think you need someone else for this. Sean Paul could probably help you out here. -Daniel > > Regards, Haixia > > On Wed, Aug 31, 2016 at 2:17 PM, Daniel Vetter <daniel at ffwll.ch> wrote: >> On Wed, Aug 31, 2016 at 11:05 PM, Daniel Vetter <daniel at ffwll.ch> wrote: >>> On Wed, Aug 31, 2016 at 10:45 PM, Haixia Shi <hshi at chromium.org> 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 -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch
