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",
(unsigned long long)start, (unsigned long long)end,
(unsigned long long)root->start,
(unsigned long long)root->end);
- else
+ dump_stack();
+ } else {
__reserve_region_with_split(root, start, end, name);
+ }
write_unlock(&resource_lock);
}
_
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