oom: dump_tasks use find_lock_task_mm too fix

When find_lock_task_mm() returns a thread other than p in dump_tasks(),
its name should be displayed instead.  This is the thread that will be
targeted by the oom killer, not its mm-less parent.

This also allows us to safely dereference task->comm without needing
get_task_comm().

While we're here, remove the cast on task_cpu(task) as Andrew suggested.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/oom_kill.c

@@ -357,10 +357,10 @@ static void dump_tasks(const struct mem_cgroup *mem)
 			continue;
 		}
 
-		printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d     %3d %s\n",
+		printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3u     %3d %s\n",
 		       task->pid, __task_cred(task)->uid, task->tgid,
 		       task->mm->total_vm, get_mm_rss(task->mm),
-		       (int)task_cpu(task), task->signal->oom_adj, p->comm);
+		       task_cpu(task), task->signal->oom_adj, task->comm);
 		task_unlock(task);
 	}
 }