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SubjectRe: [PATCH] lib/idr.c: Fix bug introduced by RCU fix
On Thu, Dec 11, 2008 at 3:17 AM, Manfred Spraul
<manfred@colorfullife.com> wrote:
> The last patch to lib/idr.c caused a bug if idr_get_new_above() was
> called on an empty idr:
> Usually, nodes stay on the same layer. New layers are added to the top
> of the tree.
> The exception is idr_get_new_above() on an empty tree: In this case,
> the new root node is first added on layer 0, then moved upwards.
> p->layer was not updated.
>
> As usual: You shall never rely on the source code comments, they
> will only mislead you.
>
> Signed-off-by: Manfred Spraul <manfred@colorfullife.com>

I've given this a run on my dri system and it appears to work great.

Tested-by: Dave Airlie <airlied@redhat.com>


> ---
> lib/idr.c | 8 +++++++-
> 1 files changed, 7 insertions(+), 1 deletions(-)
>
> diff --git a/lib/idr.c b/lib/idr.c
> index 7a785a0..1c4f928 100644
> --- a/lib/idr.c
> +++ b/lib/idr.c
> @@ -220,8 +220,14 @@ build_up:
> */
> while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
> layers++;
> - if (!p->count)
> + if (!p->count) {
> + /* special case: if the tree is currently empty,
> + * then we grow the tree by moving the top node
> + * upwards.
> + */
> + p->layer++;
> continue;
> + }
> if (!(new = get_from_free_list(idp))) {
> /*
> * The allocation failed. If we built part of
> --
> 1.5.6.5
>
>


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