On Tue, 2012-07-10 at 14:33 -0700, Andrew Morton wrote:
> On Sat, 30 Jun 2012 15:00:57 +0300
> Octavian Purdila <octavian.purd...@intel.com> wrote:
>
> > When the requested and root ranges do not intersect the logic in
> > __reserve_region_with_split will cause an infinite recursion which
> > will overflow the stack as seen in the warning bellow.
> >
> > This particular stack overflow was caused by requesting the
> > (100000000-107ffffff) range while the root range was (0-ffffffff). In
> > this case __request_resource would return the whole root range as
> > conflict range (i.e. 0-ffffffff). Then, the logic in
> > __reserve_region_with_split would continue the recursion requesting
> > the new range as (conflict->end+1, end) which incidentally in this
> > case equals the originally requested range.
> >
> > This patch aborts looking for a usable range when the requested one is
> > completely outside the root range to avoid the infinite recursion, and
> > since this indicates a problem in the layers above, it also prints an
> > error message indicating the requested and root range in order to make
> > the problem more easily traceable.
>
> I think we should also emit a stack trace so the faulty caller can be
> pinpointed.
>
> > ...
> >
> > --- a/kernel/resource.c
> > +++ b/kernel/resource.c
> > @@ -789,7 +789,13 @@ void __init reserve_region_with_split(struct resource
> > *root,
> > const char *name)
> > {
> > write_lock(&resource_lock);
> > - __reserve_region_with_split(root, start, end, name);
> > + if (start > root->end || end < root->start)
> > + pr_err("Requested range (0x%llx-0x%llx) not in root range
> > (0x%llx-0x%llx)\n",
> > + (unsigned long long)start, (unsigned long long)end,
> > + (unsigned long long)root->start,
> > + (unsigned long long)root->end);
> > + else
> > + __reserve_region_with_split(root, start, end, name);
> > write_unlock(&resource_lock);
> > }
>
> The fancy way of doing that is
>
> if (!WARN(start > root->end || end < root->start),
> "Requested range (0x%llx-0x%llx) not in root range
> (0x%llx-0x%llx)\n",
> (unsigned long long)start, (unsigned long long)end,
> (unsigned long long)root->start,
> (unsigned long long)root->end)
> __reserve_region_with_split(root, start, end, name);
>
> but that's quite the eyesore. How about doing it the simple way?
>
> ---
> a/kernel/resource.c~resource-make-sure-requested-range-intersects-root-range-fix
> +++ a/kernel/resource.c
> @@ -792,13 +792,15 @@ void __init reserve_region_with_split(st
> const char *name)
> {
> write_lock(&resource_lock);
> - if (start > root->end || end < root->start)
> + if (start > root->end || end < root->start) {
> pr_err("Requested range (0x%llx-0x%llx) not in root range
> (0x%llx-0x%llx)\n",
Maybe use %pr?
pr_err("Requested range [0x%llx-0x%llx] not in root %pr\n"
(unsigned long long)start, (unsigned long long)end,
root);
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