On 2018-01-30 12:36 PM, Nicolai Hähnle wrote: > On 30.01.2018 12:34, Michel Dänzer wrote: >> On 2018-01-30 12:28 PM, Christian König wrote: >>> Am 30.01.2018 um 12:02 schrieb Michel Dänzer: >>>> On 2018-01-30 11:40 AM, Christian König wrote: >>>>> Am 30.01.2018 um 10:43 schrieb Michel Dänzer: >>>>>> [SNIP] >>>>>>> Would it be ok to hang onto potentially arbitrary mmget references >>>>>>> essentially forever? If that's ok I think we can do your process >>>>>>> based >>>>>>> account (minus a few minor inaccuracies for shared stuff perhaps, >>>>>>> but no >>>>>>> one cares about that). >>>>>> Honestly, I think you and Christian are overthinking this. Let's try >>>>>> charging the memory to every process which shares a buffer, and go >>>>>> from >>>>>> there. >>>>> My problem is that this needs to be bullet prove. >>>>> >>>>> For example imagine an application which allocates a lot of BOs, then >>>>> calls fork() and let the parent process die. The file descriptor lives >>>>> on in the child process, but the memory is not accounted against the >>>>> child. >>>> What exactly are you referring to by "the file descriptor" here? >>> >>> The file descriptor used to identify the connection to the driver. In >>> other words our drm_file structure in the kernel. >>> >>>> What happens to BO handles in general in this case? If both parent and >>>> child process keep the same handle for the same BO, one of them >>>> destroying the handle will result in the other one not being able to >>>> use >>>> it anymore either, won't it? >>> Correct. >>> >>> That usage is actually not useful at all, but we already had >>> applications which did exactly that by accident. >>> >>> Not to mention that somebody could do it on purpose. >> >> Can we just prevent child processes from using their parent's DRM file >> descriptors altogether? Allowing it seems like a bad idea all around. > > Existing protocols pass DRM fds between processes though, don't they? > > Not child processes perhaps, but special-casing that seems like awful > design. Fair enough. Can we disallow passing DRM file descriptors which have any buffers allocated? :) -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer
