linux-kernel - [PATCH] Fix the issue that lowmemkiller fell into a cycle that try to kill a task

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Date:	Tue, 23 Sep 2014 10:57:09 +0800
From:	Hui Zhu <zhuhui@...omi.com>
To:	<gregkh@...uxfoundation.org>, <rientjes@...gle.com>,
	<vinayakm.list@...il.com>, <weijie.yang@...sung.com>
CC:	<devel@...verdev.osuosl.org>, <linux-kernel@...r.kernel.org>,
	<teawater@...il.com>, Hui Zhu <zhuhui@...omi.com>
Subject: [PATCH] Fix the issue that lowmemkiller fell into a cycle that try to kill a task

The cause of this issue is when free memroy size is low and a lot of task is
trying to shrink the memory, the task that is killed by lowmemkiller cannot get
CPU to exit itself.

Fix this issue with change the scheduling policy to SCHED_FIFO if a task's flag
is TIF_MEMDIE in lowmemkiller.

Signed-off-by: Hui Zhu <zhuhui@...omi.com>
---
 drivers/staging/android/lowmemorykiller.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
index b545d3d..ca1ffac 100644
--- a/drivers/staging/android/lowmemorykiller.c
+++ b/drivers/staging/android/lowmemorykiller.c
@@ -129,6 +129,10 @@ static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
 
 		if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
 		    time_before_eq(jiffies, lowmem_deathpending_timeout)) {
+			struct sched_param param = { .sched_priority = 1 };
+
+			if (p->policy == SCHED_NORMAL)
+				sched_setscheduler(p, SCHED_FIFO, &param);
 			task_unlock(p);
 			rcu_read_unlock();
 			return 0;
-- 
1.9.1

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