Quoting Janusz Krzysztofik (2019-04-04 11:50:14) > On Thu, 2019-04-04 at 11:43 +0100, Chris Wilson wrote: > > Quoting Janusz Krzysztofik (2019-04-04 11:40:24) > > > On Thu, 2019-04-04 at 11:28 +0100, Chris Wilson wrote: > > > > Quoting Janusz Krzysztofik (2019-04-04 11:24:45) > > > > > From: Janusz Krzysztofik <janusz.krzysztofik@xxxxxxxxx> > > > > > > > > > > In case the driver gets unbound while a device is open, kernel > > > > > panic > > > > > may be forced if a list of allocated context IDs is not empty. > > > > > > > > > > When a device is open, the list may happen to be not empty > > > > > because > > > > > a > > > > > context ID, once allocated by a context ID allocator to a > > > > > context > > > > > assosiated with that open file descriptor, is released as late > > > > > as > > > > > on device close. > > > > > > > > > > On the other hand, there is a need to release all allocated > > > > > context > > > > > IDs > > > > > and destroy the context ID allocator on driver unbind, even if > > > > > a > > > > > device > > > > > is open, in order to free memory resources consumed and prevent > > > > > from > > > > > memory leaks. The purpose of the forced kernel panic was to > > > > > protect > > > > > the context ID allocator from being silently destroyed if not > > > > > all > > > > > allocated IDs had been released. > > > > > > > > Those open fd are still pointing into kernel memory where the > > > > driver > > > > used to be. The panic is entirely correct, we should not be > > > > unloading > > > > the module before those dangling pointers have been made safe. > > > > > > > > This is papering over the symptom. How is the module being > > > > unloaded > > > > with > > > > open fd? > > > > > > A user can play with the driver unbind or device remove sysfs > > > interface. > > > > Sure, but we must still follow all the steps before _unloading_ the > > module or else the user is left pointing into reused kernel memory. > > I'm not talking about unloading the module, that is prevented by open > fds. The driver still exists after being unbound from a device and may > just respond with -ENODEV. i915_gem_contexts_fini() *is* module unload. -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
