From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752641AbbBSAVZ (ORCPT ); Wed, 18 Feb 2015 19:21:25 -0500 Received: from mail-pa0-f43.google.com ([209.85.220.43]:43374 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752478AbbBSAVX (ORCPT ); Wed, 18 Feb 2015 19:21:23 -0500 From: brian@peloton-tech.com To: mingo@redhat.com, peterz@infradead.org Cc: austin@peloton-tech.com, linux-kernel@vger.kernel.org, brian@peloton-tech.com Subject: [PATCH] sched: fix RLIMIT_RTTIME when PI-boosting to RT Date: Wed, 18 Feb 2015 16:23:56 -0800 Message-Id: <1424305436-6716-1-git-send-email-brian@peloton-tech.com> X-Mailer: git-send-email 1.7.10.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Brian Silverman When non-realtime tasks get priority-inheritance boosted to a realtime scheduling class, RLIMIT_RTTIME starts to apply to them. However, the counter used for checking this (the same one used for SCHED_RR timeslices) was not getting reset. This meant that tasks running with a non-realtime scheduling class which are repeatedly boosted to a realtime one, but never block while they are running realtime, eventually hit the timeout without ever running for a time over the limit. This patch resets the realtime timeslice counter when un-PI-boosting from an RT to a non-RT scheduling class. I have some test code with two threads and a shared PTHREAD_PRIO_INHERIT mutex which induces priority boosting and spins while boosted that gets killed by a SIGXCPU on non-fixed kernels but doesn't with this patch applied. It happens much faster with a CONFIG_PREEMPT_RT kernel, and does happen eventually with PREEMPT_VOLUNTARY kernels. Signed-off-by: Brian Silverman --- I am not subscribed to the list so please CC me on any responses. kernel/sched/core.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 87b9814..16ad0ed 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3192,6 +3192,8 @@ void rt_mutex_setprio(struct task_struct *p, int prio) } else { if (dl_prio(oldprio)) p->dl.dl_boosted = 0; + if (rt_prio(oldprio)) + p->rt.timeout = 0; p->sched_class = &fair_sched_class; } -- 1.7.10.4