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    Subject[PATCH -mm] slub: update cpu after new_slab()
    SLUB gave me a NULL pointer dereference in slab_alloc(), in the
    slab_lock(page) of its "Current cpuslab is acceptable" block: cpu
    1 had been looking at cpu_slab[2], which then went NULL beneath it.
    Since new_slab() may reenable interrupts and sleep (when __GFP_WAIT),
    we may get rescheduled on a different cpu: so need to reevaluate it.

    Signed-off-by: Hugh Dickins <hugh@veritas.com>

    --- 2.6.21-rc7-mm1/mm/slub.c 2007-04-24 20:26:48.000000000 +0100
    +++ linux/mm/slub.c 2007-04-25 15:49:12.000000000 +0100
    @@ -1234,11 +1234,12 @@ have_slab:

    page = new_slab(s, gfpflags, node);
    if (page) {
    + cpu = smp_processor_id();
    if (s->cpu_slab[cpu]) {
    /*
    - * Someone else populated the cpu_slab while
    - * we enabled interrupts. The page may not
    - * be on the requested node.
    + * Someone else populated the cpu_slab while we enabled
    + * interrupts, or we have got scheduled on another cpu.
    + * The page may not be on the requested node.
    */
    if (node == -1 ||
    page_to_nid(s->cpu_slab[cpu]) == node) {
    -
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