Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755303AbcDFNHE (ORCPT ); Wed, 6 Apr 2016 09:07:04 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34390 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754805AbcDFNHB (ORCPT ); Wed, 6 Apr 2016 09:07:01 -0400 From: Xunlei Pang To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Thomas Gleixner , Juri Lelli , Ingo Molnar , Steven Rostedt , Xunlei Pang Subject: [PATCH] rtmutex: Consider deadline tasks in try_to_take_rt_mutex() Date: Wed, 6 Apr 2016 21:06:55 +0800 Message-Id: <1459948015-13264-1-git-send-email-xlpang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1697 Lines: 51 If mutliple tasks contest try_to_take_rt_mutex(), it should let the high-priority task acquire the lock, but it misses the deadline tasks in the following condition: if (task->prio >= rt_mutex_top_waiter(lock)->prio) return 0; Deadline tasks all have "-1" prio, so above logic will always return 0, this is wrong. To solve this, we added extra deadline comparing, and let the task with smaller deadline win, or the top waiter win if equal. Signed-off-by: Xunlei Pang --- kernel/locking/rtmutex.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 244b9f3..45d2f36 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -778,11 +778,24 @@ static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task, */ if (rt_mutex_has_waiters(lock)) { /* - * If @task->prio is greater than or equal to - * the top waiter priority (kernel view), + * If !deadline @task->prio is greater than or + * equal to the top waiter priority (kernel view), * @task lost. */ - if (task->prio >= rt_mutex_top_waiter(lock)->prio) + if (task->prio >= rt_mutex_top_waiter(lock)->prio && + !dl_prio(task->prio)) + return 0; + + /* + * If the top waiter is deadline, @task must be + * deadline, otherwise did return 0 above. + * + * If @task's deadline is not smaller than the + * top waiter's, @task lost. + */ + if (dl_prio(rt_mutex_top_waiter(lock)->prio) && + !dl_time_before(task->dl.deadline, + rt_mutex_top_waiter(lock)->task->dl.deadline)) return 0; /* -- 1.8.3.1