[PATCH] oom-clear-tif_memdie-after-oom_reaper-managed-to-unmap-the-address-space-fix

[Michal Hocko]

Now that exit_oom_victim might be called on a remote task from
__oom_reap_task we have to check and clear the flag atomically
otherwise we might race and underflow oom_victims or wake up
waiters too early.

Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
 mm/oom_kill.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 7209e517adf2..8f5488345c42 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -603,7 +603,8 @@ void mark_oom_victim(struct task_struct *tsk)
  */
 void exit_oom_victim(struct task_struct *tsk)
 {
-	clear_tsk_thread_flag(tsk, TIF_MEMDIE);
+	if (!test_and_clear_tsk_thread_flag(tsk, TIF_MEMDIE))
+		return;
 
 	if (!atomic_dec_return(&oom_victims))
 		wake_up_all(&oom_victims_wait);
-- 
2.7.0.rc3

-- 
Michal Hocko
SUSE Labs