From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Subject: oom_reaper: avoid pointless atomic_inc_not_zero usage.
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().
Link: http://lkml.kernel.org/r/1465024759-8074-1-git-send-email-penguin-kernel@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/oom_kill.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
diff -puN mm/oom_kill.c~oom_reaper-avoid-pointless-atomic_inc_not_zero-usage mm/oom_kill.c
--- a/mm/oom_kill.c~oom_reaper-avoid-pointless-atomic_inc_not_zero-usage
+++ a/mm/oom_kill.c
@@ -474,14 +474,8 @@ static bool __oom_reap_task(struct task_
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)) {
_
--
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