On Tue, Aug 28, 2012 at 5:10 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Tue, Aug 28, 2012 at 10:05 AM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>>
>> Ugh. Ok, looking closer at this,
>
> Btw, looking at that code, I also found what looks like a potential
> locking bug in allocate_resource().
>
> The code does
>
>     if (new->parent)
>        .. reallocate ..
>
> to check whether a resource was already allocated. HOWEVER, it does so
> without actually holding the resource lock. Which means that
> "new->parent" might in theory change.
>
> I don't really know if we care. Anybody who does a
> "allocate_resource()" on an existing resource that might already be in
> the resource tree hopefully does *not* do that in parallel with
> another user trying to change the resource allocation, so maybe the
> right thing to do is to just say "whatever, if there is a race with
> two threads reallocating the same resource at the same time, the bug
> is a much more serious one at a higher level".

yes, another patch that that split __allocate_resource out have the similar fix.

http://git.kernel.org/?p=linux/kernel/git/yinghai/linux-yinghai.git;a=commitdiff;h=5d52b21303b7271ba4c5302b387766628f074ae2

but the changelog does not that mention the reason.

also have another version for probe_resource, please check attached version -v8.

Thanks

Yinghai