From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756224AbYDWLq4 (ORCPT ); Wed, 23 Apr 2008 07:46:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752177AbYDWLqa (ORCPT ); Wed, 23 Apr 2008 07:46:30 -0400 Received: from 75-130-111-13.dhcp.oxfr.ma.charter.com ([75.130.111.13]:44311 "EHLO novell1.haskins.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751854AbYDWLq3 (ORCPT ); Wed, 23 Apr 2008 07:46:29 -0400 From: Gregory Haskins Subject: [PATCH 1/2] sched: fix RT task-wakeup logic To: Ingo Molnar Cc: Gregory Haskins , Dmitry Adamushko , Steven Rostedt , linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org Date: Wed, 23 Apr 2008 07:13:29 -0400 Message-ID: <20080423111329.4981.88455.stgit@novell1.haskins.net> In-Reply-To: <20080423111313.4981.37345.stgit@novell1.haskins.net> References: <20080423111313.4981.37345.stgit@novell1.haskins.net> User-Agent: StGIT/0.12.1 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dmitry Adamushko pointed out a logic error in task_wake_up_rt() where we will always evaluate to "true". You can find the thread here: http://lkml.org/lkml/2008/4/22/296 In reality, we only want to try to push tasks away when a wake up request is not going to preempt the current task. So lets fix it. Note: We introduce test_tsk_need_resched() instead of open-coding the flag check so that the merge-conflict with -rt should help remind us that we may need to support NEEDS_RESCHED_DELAYED in the future, too. Signed-off-by: Gregory Haskins CC: Dmitry Adamushko CC: Ingo Molnar CC: Steven Rostedt --- include/linux/sched.h | 7 ++++++- kernel/sched_rt.c | 7 +++++-- 2 files changed, 11 insertions(+), 3 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 949bd54..55d4bd4 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1966,6 +1966,11 @@ static inline void clear_tsk_need_resched(struct task_struct *tsk) clear_tsk_thread_flag(tsk,TIF_NEED_RESCHED); } +static inline int test_tsk_need_resched(struct task_struct *tsk) +{ + return unlikely(test_tsk_thread_flag(tsk,TIF_NEED_RESCHED)); +} + static inline int signal_pending(struct task_struct *p) { return unlikely(test_tsk_thread_flag(p,TIF_SIGPENDING)); @@ -1980,7 +1985,7 @@ static inline int fatal_signal_pending(struct task_struct *p) static inline int need_resched(void) { - return unlikely(test_thread_flag(TIF_NEED_RESCHED)); + return unlikely(test_tsk_need_resched(current)); } /* diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 79e5ad5..ae6b0e6 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -1058,11 +1058,14 @@ static void post_schedule_rt(struct rq *rq) } } - +/* + * If we are not running and we are not going to reschedule soon, we should + * try to push tasks away now + */ static void task_wake_up_rt(struct rq *rq, struct task_struct *p) { if (!task_running(rq, p) && - (p->prio >= rq->rt.highest_prio) && + !test_tsk_need_resched(rq->curr) && rq->rt.overloaded) push_rt_tasks(rq); }