oom: check PF_KTHREAD instead of !mm to skip kthreads

select_bad_process() thinks a kernel thread can't have ->mm != NULL, this
is not true due to use_mm().

Change the code to check PF_KTHREAD.

Reviewed-by: KAMEZAWA Hiroyuki <[email protected]>
Signed-off-by: Oleg Nesterov <[email protected]>
Signed-off-by: David Rientjes <[email protected]>
Acked-by: KOSAKI Motohiro <[email protected]>
Cc: Balbir Singh <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: oleg-nesterov

mm/oom_kill.c

@@ -256,14 +256,11 @@ static struct task_struct *select_bad_process(unsigned long *ppoints,
 	for_each_process(p) {
 		unsigned long points;
 
-		/*
-		 * skip kernel threads and tasks which have already released
-		 * their mm.
-		 */
+		/* skip tasks that have already released their mm */
 		if (!p->mm)
 			continue;
-		/* skip the init task */
-		if (is_global_init(p))
+		/* skip the init task and kthreads */
+		if (is_global_init(p) || (p->flags & PF_KTHREAD))
 			continue;
 		if (mem && !task_in_mem_cgroup(p, mem))
 			continue;