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From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: akpm@linux-foundation.org
Cc: linux-mm@kvack.org,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
	Michal Hocko <mhocko@suse.com>, Arnd Bergmann <arnd@arndb.de>
Subject: [PATCH] oom_reaper: avoid pointless atomic_inc_not_zero usage.
Date: Sat,  4 Jun 2016 16:19:19 +0900
Message-ID: <1465024759-8074-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> (raw)

Since commit 36324a990cf578b5 ("oom: clear TIF_MEMDIE after oom_reaper
managed to unmap the address space") changed to use find_lock_task_mm()
for finding a mm_struct to reap, it is guaranteed that mm->mm_users > 0
because find_lock_task_mm() returns a task_struct with ->mm != NULL.
Therefore, we can safely use atomic_inc().

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 mm/oom_kill.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index dfb1ab6..8050fa0 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -474,13 +474,8 @@ static bool __oom_reap_task(struct task_struct *tsk)
 	p = find_lock_task_mm(tsk);
 	if (!p)
 		goto unlock_oom;
-
 	mm = p->mm;
-	if (!atomic_inc_not_zero(&mm->mm_users)) {
-		task_unlock(p);
-		goto unlock_oom;
-	}
-
+	atomic_inc(&mm->mm_users);
 	task_unlock(p);
 
 	if (!down_read_trylock(&mm->mmap_sem)) {
-- 
1.8.3.1

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Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-04  7:19 Tetsuo Handa [this message]
2016-06-06  7:18 ` Michal Hocko
2016-06-06 21:13 ` Andrew Morton
2016-06-08 17:04   ` Andrew Morton
2016-06-08 22:27     ` Tetsuo Handa

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