mm,oom_reaper: remove pointless kthread_run() error check

Since oom_init() is called before userspace processes start, memory
allocation failure for creating the OOM reaper kernel thread will let
the OOM killer call panic() rather than wake up the OOM reaper.

Link: http://lkml.kernel.org/r/1510137800-4602-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/oom_kill.c

@@ -640,9 +640,6 @@ static int oom_reaper(void *unused)
 
 static void wake_oom_reaper(struct task_struct *tsk)
 {
-	if (!oom_reaper_th)
-		return;
-
 	/* tsk is already queued? */
 	if (tsk == oom_reaper_list || tsk->oom_reaper_list)
 		return;
@@ -660,11 +657,6 @@ static void wake_oom_reaper(struct task_struct *tsk)
 static int __init oom_init(void)
 {
 	oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
-	if (IS_ERR(oom_reaper_th)) {
-		pr_err("Unable to start OOM reaper %ld. Continuing regardless\n",
-				PTR_ERR(oom_reaper_th));
-		oom_reaper_th = NULL;
-	}
 	return 0;
 }
 subsys_initcall(oom_init)