On Thu, Dec 19, 2019 at 12:32 PM Gerd Hoffmann <kraxel@xxxxxxxxxx> wrote: > > Hi, > > > > Like I said, for most drivers > > > > you can pretty much assume that their unload sequence has been broken > > > > since forever. It's not often tested, and especially the hotunbind > > > > from a device (as opposed to driver unload) stuff wasn't even possible > > > > to get right until just recently. > > > > > > Do you think it's worth trying to fix this for 5.5 and earlier, or just > > > switch to the device-managed interface for 5.6 and forget about 5.5 and > > > earlier? > > > > I suspect it's going to be quite some trickery to fix this properly > > and everywhere, even for just one driver. Lots of drm drivers > > unfortunately use anti-patterns with wrong lifetimes (e.g. you can't > > use devm_kmalloc for anything that hangs of a drm_device, like > > plane/crtc/connector). Except when it's for a real hotunpluggable > > device (usb) we've never bothered backporting these fixes. Too much > > broken stuff unfortunately. > > While being at it: How would a driver cleanup properly cleanup gem > objects created by userspace on hotunbind? Specifically a gem object > pinned to vram? Two things: - the mmap needs to be torn down and replaced by something which will sigbus. Probably should have that as a helper (plus vram fault code should use drm_dev_enter/exit to plug races). - otherwise all datastructures need to be properly refcounted. drm_device now is (if your driver isn't broken), but any dma_fence or dma_buf we create and export has an independent lifetime, and currently the refcounting for is still wobbly I think. So some work to do, both in helpers/core code and in drivers to get updated. -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
