linux-kernel - [PATCH 7/8] Use TASK_KILLABLE instead TASK

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Message-Id: <20091214213145.BBC3.A69D9226@jp.fujitsu.com>
Date:	Mon, 14 Dec 2009 21:32:18 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	kosaki.motohiro@...fujitsu.com, lwoodman@...hat.com,
	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, minchan.kim@...il.com
Subject: [PATCH 7/8] Use TASK_KILLABLE instead TASK_UNINTERRUPTIBLE

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@...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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