[PATCH 2/2] android, lmk: Reverse the order of setting TIF_MEMDIE and sending SIGKILL.

[Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>]

Hello.

Should selected_tasksize be added to rem even when TIF_MEMDIE was not set?

Please see a thread from http://www.spinics.net/lists/linux-mm/msg93246.html
if you want to know why to reverse the order.
----------------------------------------
>From 2d4cc11d8128e4c1397631b91fea78da3eaefb47 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Wed, 26 Aug 2015 20:52:39 +0900
Subject: [PATCH 2/2] android, lmk: Reverse the order of setting TIF_MEMDIE and sending SIGKILL.

If we set TIF_MEMDIE before sending SIGKILL, memory reserves could be
spent for allocations which are not needed for terminating the victim.
Reverse the order as with oom_kill_process() does.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
 drivers/staging/android/lowmemorykiller.c | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
index d5d25e4..c39b6a2 100644
--- a/drivers/staging/android/lowmemorykiller.c
+++ b/drivers/staging/android/lowmemorykiller.c
@@ -156,26 +156,24 @@ next:
 	}
 	if (selected) {
 		task_lock(selected);
-		if (!selected->mm) {
-			/* Already exited, cannot do mark_tsk_oom_victim() */
-			task_unlock(selected);
-			goto out;
-		}
+		lowmem_print(1, "send sigkill to %d (%s), adj %hd, size %d\n",
+			     selected->pid, selected->comm,
+			     selected_oom_score_adj, selected_tasksize);
+		task_unlock(selected);
+		send_sig(SIGKILL, selected, 0);
 		/*
 		 * FIXME: lowmemorykiller shouldn't abuse global OOM killer
 		 * infrastructure. There is no real reason why the selected
 		 * task should have access to the memory reserves.
 		 */
-		mark_oom_victim(selected);
-		lowmem_print(1, "send sigkill to %d (%s), adj %hd, size %d\n",
-			     selected->pid, selected->comm,
-			     selected_oom_score_adj, selected_tasksize);
+		task_lock(selected);
+		if (selected->mm) {
+			mark_oom_victim(selected);
+			lowmem_deathpending_timeout = jiffies + HZ;
+			rem += selected_tasksize;
+		}
 		task_unlock(selected);
-		lowmem_deathpending_timeout = jiffies + HZ;
-		send_sig(SIGKILL, selected, 0);
-		rem += selected_tasksize;
 	}
-out:
 	lowmem_print(4, "lowmem_scan %lu, %x, return %lu\n",
 		     sc->nr_to_scan, sc->gfp_mask, rem);
 	rcu_read_unlock();
-- 
1.8.3.1

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