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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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