From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755316AbbDTOwc (ORCPT ); Mon, 20 Apr 2015 10:52:32 -0400 Received: from smtprelay0151.hostedemail.com ([216.40.44.151]:37008 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753342AbbDTOwb (ORCPT ); Mon, 20 Apr 2015 10:52:31 -0400 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Spam-Summary: 2,0,0,,d41d8cd98f00b204,rostedt@goodmis.org,:::::::::,RULES_HIT:41:355:379:541:599:800:960:973:988:989:1260:1277:1311:1313:1314:1345:1359:1437:1515:1516:1518:1534:1541:1593:1594:1711:1730:1747:1777:1792:2393:2553:2559:2562:2692:3138:3139:3140:3141:3142:3151:3353:3622:3865:3866:3867:3870:3871:3872:3874:5007:6120:6261:7875:7901:7903:7974:10004:10400:10848:10967:11026:11232:11658:11914:12043:12296:12438:12517:12519:12740:13069:13161:13229:13255:13311:13357:14096:14097:21080,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:none,Custom_rules:0:0:0 X-HE-Tag: line56_4ff191ef37901 X-Filterd-Recvd-Size: 2442 Date: Mon, 20 Apr 2015 10:52:28 -0400 From: Steven Rostedt To: Xunlei Pang Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Juri Lelli , Xunlei Pang Subject: Re: [PATCH v6 2/3] sched/rt: Fix wrong SMP scheduler behavior for equal prio cases Message-ID: <20150420105228.461e103c@gandalf.local.home> In-Reply-To: <1429518168-7965-2-git-send-email-xlpang@126.com> References: <1429518168-7965-1-git-send-email-xlpang@126.com> <1429518168-7965-2-git-send-email-xlpang@126.com> X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.25; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 20 Apr 2015 16:22:47 +0800 Xunlei Pang wrote: > static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p) > { > } > @@ -1506,8 +1526,21 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p) > * The previous task needs to be made eligible for pushing > * if it is still active > */ > - if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1) > - enqueue_pushable_task(rq, p); > + if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1) { > + /* > + * put_prev_task_rt() is called by many functions, > + * pick_next_task_rt() is the only one may have > + * PREEMPT_ACTIVE set. So if detecting p(current > + * task) is preempted in such case, we should > + * enqueue it to the front of the pushable plist, > + * as there may be multiple tasks with the same > + * priority as p. The above comment is very difficult to understand. Maybe something like: /* * When put_prev_task_rt() is called by * pick_next_task_rt(), if PREEMPT_ACTIVE is set, it * means that the current rt task is being preempted by * a higher priority task. To maintain FIFO, it must * stay ahead of any other task that is queued at the * same priority. */ -- Steve > + */ > + if (preempt_count() & PREEMPT_ACTIVE) > + enqueue_pushable_task_preempted(rq, p); > + else > + enqueue_pushable_task(rq, p); > + } > } > > #ifdef CONFIG_SMP