Messages in this thread |  | | Subject | Re: [PATCH v2] mm: cma: support sysfs | From | John Hubbard <> | Date | Tue, 9 Feb 2021 12:11:20 -0800 |
| |
On 2/9/21 9:49 AM, Greg KH wrote: >>> That's fine if you want to add it to the parent. If so, then the >>> kobject controls the lifetime of the structure, nothing else can. >> >> The problem was parent object(i.e., struct cma cma_areas) is >> static arrary so kobj->release function will be NULL or just >> dummy. Is it okay? I thought it was one of the what you wanted >> to avoid it. > > No, that is not ok. > >>> Either is fine with me, what is "forbidden" is having a kobject and >>> somehow thinking that it does not control the lifetime of the structure. >> >> Since parent object is static arrary, there is no need to control the >> lifetime so I am curious if parent object approach is okay from kobject >> handling point of view. > > So the array is _NEVER_ freed? If not, fine, don't provide a release > function for the kobject, but ick, just make a dynamic kobject I don't > see the problem for something so tiny and not very many... >
Yeah, I wasn't trying to generate so much discussion, I initially thought it would be a minor comment: "just use an embedded struct and avoid some extra code", at first.
> I worry that any static kobject might be copied/pasted as someone might > think this is an ok thing to do. And it's not an ok thing to do. >
Overall, then, we're seeing that there is a small design hole: in order to use sysfs most naturally, you either much provide a dynamically allocated item for it, or you must use the static kobject, and the second one sets a bad example.
I think we should just use a static kobject, with a cautionary comment to would-be copy-pasters, that explains the design constraints above. That way, we still get a nice, less-code implementation, a safe design, and it only really costs us a single carefully written comment.
thanks, -- John Hubbard NVIDIA
|  |