Quoting Janusz Krzysztofik (2019-04-04 11:24:45)
From: Janusz Krzysztofik janusz.krzysztofik@intel.com
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? If all the fd have been closed, how have we failed to flush and retire all requests (thereby unpinning the contexts and all other pointers). -Chris