From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CD4E6ECDFB1 for ; Sun, 15 Jul 2018 23:26:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8E189208DB for ; Sun, 15 Jul 2018 23:26:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8E189208DB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zytor.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727538AbeGOXuW (ORCPT ); Sun, 15 Jul 2018 19:50:22 -0400 Received: from terminus.zytor.com ([198.137.202.136]:52477 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727005AbeGOXuW (ORCPT ); Sun, 15 Jul 2018 19:50:22 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id w6FNOqio920883 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Sun, 15 Jul 2018 16:24:52 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id w6FNOqO0920880; Sun, 15 Jul 2018 16:24:52 -0700 Date: Sun, 15 Jul 2018 16:24:52 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Juri Lelli Message-ID: Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, hpa@zytor.com, mark.rutland@arm.com, mingo@kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, juri.lelli@redhat.com, luca.abeni@santannapisa.it, bristot@redhat.com Reply-To: hpa@zytor.com, tglx@linutronix.de, linux-kernel@vger.kernel.org, bristot@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, luca.abeni@santannapisa.it, mark.rutland@arm.com, mingo@kernel.org, torvalds@linux-foundation.org In-Reply-To: <20180711072948.27061-1-juri.lelli@redhat.com> References: <20180711072948.27061-1-juri.lelli@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] sched/deadline: Fix switched_from_dl() warning Git-Commit-ID: e117cb52bdb4d376b711bee34af6434c9e314b3b X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: e117cb52bdb4d376b711bee34af6434c9e314b3b Gitweb: https://git.kernel.org/tip/e117cb52bdb4d376b711bee34af6434c9e314b3b Author: Juri Lelli AuthorDate: Wed, 11 Jul 2018 09:29:48 +0200 Committer: Ingo Molnar CommitDate: Sun, 15 Jul 2018 23:47:33 +0200 sched/deadline: Fix switched_from_dl() warning Mark noticed that syzkaller is able to reliably trigger the following warning: dl_rq->running_bw > dl_rq->this_bw WARNING: CPU: 1 PID: 153 at kernel/sched/deadline.c:124 switched_from_dl+0x454/0x608 Kernel panic - not syncing: panic_on_warn set ... CPU: 1 PID: 153 Comm: syz-executor253 Not tainted 4.18.0-rc3+ #29 Hardware name: linux,dummy-virt (DT) Call trace: dump_backtrace+0x0/0x458 show_stack+0x20/0x30 dump_stack+0x180/0x250 panic+0x2dc/0x4ec __warn_printk+0x0/0x150 report_bug+0x228/0x2d8 bug_handler+0xa0/0x1a0 brk_handler+0x2f0/0x568 do_debug_exception+0x1bc/0x5d0 el1_dbg+0x18/0x78 switched_from_dl+0x454/0x608 __sched_setscheduler+0x8cc/0x2018 sys_sched_setattr+0x340/0x758 el0_svc_naked+0x30/0x34 syzkaller reproducer runs a bunch of threads that constantly switch between DEADLINE and NORMAL classes while interacting through futexes. The splat above is caused by the fact that if a DEADLINE task is setattr back to NORMAL while in non_contending state (blocked on a futex - inactive timer armed), its contribution to running_bw is not removed before sub_rq_bw() gets called (!task_on_rq_queued() branch) and the latter sees running_bw > this_bw. Fix it by removing a task contribution from running_bw if the task is not queued and in non_contending state while switched to a different class. Reported-by: Mark Rutland Signed-off-by: Juri Lelli Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Daniel Bristot de Oliveira Reviewed-by: Luca Abeni Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: claudio@evidence.eu.com Cc: rostedt@goodmis.org Link: http://lkml.kernel.org/r/20180711072948.27061-1-juri.lelli@redhat.com Signed-off-by: Ingo Molnar --- kernel/sched/deadline.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index fbfc3f1d368a..10c7b51c0d1f 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2290,8 +2290,17 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p) if (task_on_rq_queued(p) && p->dl.dl_runtime) task_non_contending(p); - if (!task_on_rq_queued(p)) + if (!task_on_rq_queued(p)) { + /* + * Inactive timer is armed. However, p is leaving DEADLINE and + * might migrate away from this rq while continuing to run on + * some other class. We need to remove its contribution from + * this rq running_bw now, or sub_rq_bw (below) will complain. + */ + if (p->dl.dl_non_contending) + sub_running_bw(&p->dl, &rq->dl); sub_rq_bw(&p->dl, &rq->dl); + } /* * We cannot use inactive_task_timer() to invoke sub_running_bw()