From 491a1c65ae498dea0e39b24a46e528a78a8532ed Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Fri, 24 Jun 2016 14:48:35 -0700 Subject: mm,oom_reaper: don't call mmput_async() without atomic_inc_not_zero() Commit e2fe14564d33 ("oom_reaper: close race with exiting task") reduced frequency of needlessly selecting next OOM victim, but was calling mmput_async() when atomic_inc_not_zero() failed. Link: http://lkml.kernel.org/r/1464423365-5555-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp Signed-off-by: Tetsuo Handa Acked-by: Michal Hocko Cc: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/oom_kill.c | 1 + 1 file changed, 1 insertion(+) (limited to 'mm/oom_kill.c') diff --git a/mm/oom_kill.c b/mm/oom_kill.c index acbc432d1a52..be67df3b6569 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -478,6 +478,7 @@ static bool __oom_reap_task(struct task_struct *tsk) mm = p->mm; if (!atomic_inc_not_zero(&mm->mm_users)) { task_unlock(p); + mm = NULL; goto unlock_oom; } -- cgit v1.2.3 From 9df10fb7b80bc2f540956ba01b5e7ee1012001a5 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Fri, 24 Jun 2016 14:48:38 -0700 Subject: oom_reaper: avoid pointless atomic_inc_not_zero usage. Since commit 36324a990cf5 ("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(). Link: http://lkml.kernel.org/r/1465024759-8074-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp Signed-off-by: Tetsuo Handa Acked-by: Michal Hocko Cc: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/oom_kill.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) (limited to 'mm/oom_kill.c') diff --git a/mm/oom_kill.c b/mm/oom_kill.c index be67df3b6569..ddf74487f848 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -474,14 +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); - mm = NULL; - goto unlock_oom; - } - + atomic_inc(&mm->mm_users); task_unlock(p); if (!down_read_trylock(&mm->mmap_sem)) { -- cgit v1.2.3