mm/oom_kill.c: fix task_will_free_mem() comment

Attempt to demystify the task_will_free_mem() loop.

Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/oom_kill.c

@@ -803,8 +803,9 @@ static bool task_will_free_mem(struct task_struct *task)
 		return true;
 
 	/*
-	 * This is really pessimistic but we do not have any reliable way
-	 * to check that external processes share with our mm
+	 * Make sure that all tasks which share the mm with the given tasks
+	 * are dying as well to make sure that a) nobody pins its mm and
+	 * b) the task is also reapable by the oom reaper.
 	 */
 	rcu_read_lock();
 	for_each_process(p) {