Re: [PATCH] mce: fix warning messages about static struct mce_device
From: Alan Stern
Date: Thu Jan 19 2012 - 15:52:19 EST
On Thu, 19 Jan 2012, Ingo Molnar wrote:
>
> * Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
>
> > Or to put it another way, even though no code takes references
> > to these device structures (can you really guarantee that even
> > now?), [...]
>
> That's a good question. Do these devices get exposed to
> user-space access via sysfs somehow, where such an extra
> reference could materialize?
_Every_ struct device that gets registered is exposed to userspace via
sysfs. Of course, that doesn't mean the exposure can create extra
references.
> > [...] how do you prevent references being taken in future
> > versions of the kernel? Calling memset while there still are
> > outstanding references very definitely _is_ a bug.
>
> Unless there's a reference i missed the 'refcounting' here is
> very simple and does not exist at all.
>
> IMHO you should not impose complexity and abstraction on code
> just because. Now i don't care much about the extra pointer, but
> the [NR_CPUS] array was doubly ugly (and Greg promised to fix
> that, so no problems from me).
>
> So the conclusion is that the reasons stated here don't really
> apply. The one i mentioned *does* apply: the original bug was
> due to sloppy life time rules of this driver buffer, and that
> came back to bite us. Making it dynamic solves that kind of
> problem. In that sense the warning is fine too.
Then it looks like we are in agreement. :-)
Alan Stern
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