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    Subject[PATCH 7/8] Use TASK_KILLABLE instead TASK_UNINTERRUPTIBLE
    Date
    When fork bomb invoke OOM Killer, almost task might start to reclaim and
    sleep on shrink_zone_begin(). if we use TASK_UNINTERRUPTIBLE, OOM killer
    can't kill such task. it mean we never recover from fork bomb.

    This patch fixes it.

    Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    ---
    mm/vmscan.c | 20 +++++++++++++-------
    1 files changed, 13 insertions(+), 7 deletions(-)

    diff --git a/mm/vmscan.c b/mm/vmscan.c
    index bf229d3..e537361 100644
    --- a/mm/vmscan.c
    +++ b/mm/vmscan.c
    @@ -1618,7 +1618,10 @@ static int shrink_zone_begin(struct zone *zone, struct scan_control *sc)
    * we would just make things slower.
    */
    for (;;) {
    - prepare_to_wait_exclusive(wq, &wait, TASK_UNINTERRUPTIBLE);
    + prepare_to_wait_exclusive(wq, &wait, TASK_KILLABLE);
    +
    + if (fatal_signal_pending(current))
    + goto stop_reclaim;

    if (atomic_read(&zone->concurrent_reclaimers) <=
    max_zone_concurrent_reclaimers)
    @@ -1631,18 +1634,21 @@ static int shrink_zone_begin(struct zone *zone, struct scan_control *sc)
    * break out of the loop and go back to the allocator.
    */
    if (zone_watermark_ok(zone, sc->order, low_wmark_pages(zone),
    - 0, 0)) {
    - wake_up_all(wq);
    - finish_wait(wq, &wait);
    - sc->nr_reclaimed += sc->nr_to_reclaim;
    - return -ERESTARTSYS;
    - }
    + 0, 0))
    + goto found_lots_memory;
    }
    finish_wait(wq, &wait);

    out:
    atomic_inc(&zone->concurrent_reclaimers);
    return 0;
    +
    + found_lots_memory:
    + wake_up_all(wq);
    + stop_reclaim:
    + finish_wait(wq, &wait);
    + sc->nr_reclaimed += sc->nr_to_reclaim;
    + return -ERESTARTSYS;
    }

    static void shrink_zone_end(struct zone *zone, struct scan_control *sc)
    --
    1.6.5.2




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