On Fri, Sep 07, 2012 at 04:08:19PM -0600, T Makphaibulchoke wrote:
> Using recurvise call to try adding a non-conflicting region in the function
> __reserve_region_with_split() could result in a stack overflow in the case
> that the recursive calls are too deep. Convert the recursive calls to
> an iterative loop to avoid the problem.
>
> Tested on a machine containing 135 regions. The kernel no longer panicked
> with stack overflow.
>
> Also tested with code arbitrarily adding regions with no conflict, embedding
> two consecutive conflicts and embedding two non-consecutive conflicts.
>
> Signed-off-by: T Makphaibulchoke <t...@hp.com>
>
> ---
> Change since v2:
> * Initializing both the name and flags fileds of the newly allocated region
> request.
>
> Change since v1:
> * Fixing __resrve_region_with_split() to ensure a reqion reserve request is
> satisfied to the fullest extent, minus any overlapping conflicting regions.
> ---
> kernel/resource.c | 50 ++++++++++++++++++++++++++++++++++++++------------
> 1 files changed, 38 insertions(+), 12 deletions(-)
>
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 34d4588..73f35d4 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -763,6 +763,7 @@ static void __init __reserve_region_with_split(struct
> resource *root,
> struct resource *parent = root;
> struct resource *conflict;
> struct resource *res = kzalloc(sizeof(*res), GFP_ATOMIC);
> + struct resource *next_res = NULL;
>
> if (!res)
> return;
> @@ -772,21 +773,46 @@ static void __init __reserve_region_with_split(struct
> resource *root,
> res->end = end;
> res->flags = IORESOURCE_BUSY;
>
> - conflict = __request_resource(parent, res);
> - if (!conflict)
> - return;
> + while (1) {
>
> - /* failed, split and try again */
> - kfree(res);
> + conflict = __request_resource(parent, res);
> + if (!conflict) {
> + if (!next_res)
> + break;
> + res = next_res;
> + next_res = NULL;
> + continue;
> + }
>
> - /* conflict covered whole area */
> - if (conflict->start <= start && conflict->end >= end)
> - return;
> + /* conflict covered whole area */
> + if (conflict->start <= res->start &&
> + conflict->end >= res->end) {
> + kfree(res);
> + WARN_ON(next_res);
> + break;
> + }
> +
> + /* failed, split and try again */
> + if (conflict->start > res->start) {
> + end = res->end;
> + res->end = conflict->start - 1;
> + if (conflict->end < end) {
> + next_res = kzalloc(sizeof(*next_res),
> + GFP_ATOMIC);
> + if (!next_res) {
> + kfree(res);
> + break;
> + }
> + next_res->name = name;
> + next_res->start = conflict->end + 1;
> + next_res->end = end;
> + next_res->flags = IORESOURCE_BUSY;
> + }
> + } else {
> + res->start = conflict->end + 1;
> + }
> + }
>
> - if (conflict->start > start)
> - __reserve_region_with_split(root, start, conflict->start-1,
> name);
> - if (conflict->end < end)
> - __reserve_region_with_split(root, conflict->end+1, end, name);
> }
>
> void __init reserve_region_with_split(struct resource *root,
Reviewed-by: Ram Pai <linux...@us.ibm.com>
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