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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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