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. Cheers, Nicolai -- Lerne, wie die Welt wirklich ist, Aber vergiss niemals, wie sie sein sollte.
