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    Subject[PATCH] do not free non slab allocated per_cpu_pageset
    On Thu, 21 Sep 2006, David Rientjes wrote:

    > The _only_ time zone_pcp is slab allocated is through process_zones(). So
    > if we have an error on kmalloc_node for that zone_pcp, all previous
    > allocations are freed and process_zones() fails for that cpu.
    > We are guaranteed that the process_zones() for cpu 0 succeeds, otherwise
    > the pageset notifier isn't registered. On CPU_UP_PREPARE for cpu 4 in
    > this case, process_zones() fails because we couldn't kmalloc the
    > per_cpu_pageset and we return NOTIFY_BAD. This prints the failed message
    > in the report and then CPU_UP_CANCELED is sent back to the notifier which
    > attempts to kfree the zone that was never kmalloc'd.
    > The fix will work except for the case that zone_pcp is never set to NULL
    > as it should be.

    As reported by Keith, the following 2.6.18 patch stops the panic
    associated with attempting to free a non slab-allocated per_cpu_pageset.

    Signed-off-by: David Rientjes <>
    mm/page_alloc.c | 4 +++-
    1 files changed, 3 insertions(+), 1 deletions(-)

    diff --git a/mm/page_alloc.c b/mm/page_alloc.c
    index 54a4f53..e16173f 100644
    --- a/mm/page_alloc.c
    +++ b/mm/page_alloc.c
    @@ -1845,8 +1845,10 @@ static inline void free_zone_pagesets(in
    for_each_zone(zone) {
    struct per_cpu_pageset *pset = zone_pcp(zone, cpu);

    + /* Free per_cpu_pageset if it is slab allocated */
    + if (pset != &boot_pageset[cpu])
    + kfree(pset);
    zone_pcp(zone, cpu) = NULL;
    - kfree(pset);

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      Last update: 2006-09-22 20:23    [W:0.021 / U:0.316 seconds]
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