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=-4.0 required=3.0 tests=FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_PASS 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 740A3C43381 for ; Mon, 25 Feb 2019 17:41:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4DB69213A2 for ; Mon, 25 Feb 2019 17:41:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728767AbfBYRlP (ORCPT ); Mon, 25 Feb 2019 12:41:15 -0500 Received: from mout.gmx.net ([212.227.15.15]:56885 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725936AbfBYRlP (ORCPT ); Mon, 25 Feb 2019 12:41:15 -0500 Received: from homer.simpson.net ([185.221.150.179]) by mail.gmx.com (mrgmx002 [212.227.17.190]) with ESMTPSA (Nemesis) id 0ML72n-1gybMC1bMX-000PQE; Mon, 25 Feb 2019 18:40:37 +0100 Message-ID: <1551116436.5281.5.camel@gmx.de> Subject: Re: [PATCH RT 4/2] hrtimer: Don't lose state in cpu_chill() From: Mike Galbraith To: Sebastian Andrzej Siewior Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Steven Rostedt , Peter Zijlstra Date: Mon, 25 Feb 2019 18:40:36 +0100 In-Reply-To: <20190225163440.ptw2ohijokhumn7i@linutronix.de> References: <20190218163107.iwdpngwmbs6xyk7x@linutronix.de> <20190218163137.cmor4ek3odus5m6j@linutronix.de> <20190219160755.fn4c65ph4lzqflw2@linutronix.de> <20190219160842.qxpwicoa5tzq4njo@linutronix.de> <1551105815.6234.14.camel@gmx.de> <20190225163440.ptw2ohijokhumn7i@linutronix.de> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Provags-ID: V03:K1:82esocUz6gOqNxMOqU10sQzm04DmWmYIzqTaGaLNzrzhpMUe0Vv D5+Valuv+xa2Qtg3yL3o7Y5CD16iZ2dUdTwmpAth2L8tm2N7ddJPPq9w9je1rO5kpt3GvmS uXSMTnW0zugg8ib97emuDPW4o3F20MhgMW/d0auEeYT1k1EeyQGvdSyltHICdiWa0demT3s XWsokB400M83xuoVil7nQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:n3rKK/JSzVs=:tWdncV7Yd5P65zVPpdXbvf mrGrCBiNeiSLBP5pk97ILzqZ4iLjymaDtLiOH8yAGEG3nurQo6n9c6+qntdbcvVJlIS+cygxz MtcjLxGh0ZPgjUdcYHdU3QnhzUkZ5By3kqBzxff0K5yqt7YKiaOYeNt5ZhSqVk6y+TJKGzc2c FZPkiZY6S3DbHlLK4beug0zxLuVdE9KqoFdgN+mCN5fcyxytqfsAUz5a1crOIDaFEKkpw2Ue4 7ABLD+XbEWMOT04XI9YnaQ68/Fhwm7zWVn0e+XU5SiwUStvvFXTPazrNfom1HIdD7buuuXSwT CDxZ/yiNQxBKBK+V4c/xGXaONXjAIs930CnB9g9A1oRcHrnyUno9C9oPbmuU3x0WMnx9+I/0b 2LGwfe7OsXT+X+Vlb6DF39r5i8X8zIx37eaDib/AqMA4mTVDg/9kFx1mKIZ1UtqAvQumxCjN/ b3OnsBrclh/1Z39E+SySy89NFouzpNVitowh2Kq1uyw1ADgOv3MqumAoQ7qo3lNWvZF4fzMeE VOVClX/Da7parPXJgP3jGE6QpXbSwKCAQsLtDLY1YMKd4rOdM5KII5HIx0KYymhs2RBr2UF1e Yaq2vblqjhdXQY/juOgHTSvFGBVaQ2mh1qzmuIoJJ8Cj0tVtV/UuFImy56JNXntu8fQOx41+t VUPOaKOEruH4fBaGdNyQE3F6sxvX7DfHToSaVill+4+vTraRBC1JECHz50IOnyzsQc7sDuh1E 0IeSqIl3GulhR0yJugsf45gKvThemJfd/zucRvJEoeUuEraWBfBIt6g7jMiUAqePMW90tcBGg V97tg5ipHtZ1z6GaxX/iMk80jp/yEuJUVsYuE2pXWkMYPNqBVPNsP1yE4XvuEYVL4M+t5uIPQ OcXSNoFWAaywhU1tR9LqJ2eGAw+KA1qvZlsgGqr23ln4fPIIfDE7gDGllHQfWv Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2019-02-25 at 17:34 +0100, Sebastian Andrzej Siewior wrote: > On 2019-02-25 15:43:35 [+0100], Mike Galbraith wrote: > > Hi Sebastian, > Hi Mike, > > > My box claims that this patch is busted. It argues its case by IO > > deadlocking any kernel this patch is applied to when spinning rust is > > flogged, including virgin 4.19-rt14, said kernel becoming stable again > > when I whack the accused. > > does the following hunk make any difference? Ah. Yup, box says you're right. > diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c > index 6ecdb9469ca9..e154632b90b4 100644 > --- a/kernel/time/hrtimer.c > +++ b/kernel/time/hrtimer.c > @@ -1884,20 +1884,29 @@ COMPAT_SYSCALL_DEFINE2(nanosleep, struct old_timespec32 __user *, rqtp, > */ > void cpu_chill(void) > { > + struct task_struct *self = current; > ktime_t chill_time; > unsigned int freeze_flag = current->flags & PF_NOFREEZE; > - long saved_state; > > - saved_state = current->state; > - chill_time = ktime_set(0, NSEC_PER_MSEC); > + raw_spin_lock_irq(&self->pi_lock); > + WARN_ON(self->saved_state != TASK_RUNNING); > + self->saved_state = self->state; > __set_current_state_no_track(TASK_UNINTERRUPTIBLE); > + raw_spin_unlock_irq(&self->pi_lock); > + > + chill_time = ktime_set(0, NSEC_PER_MSEC); > + > current->flags |= PF_NOFREEZE; > sleeping_lock_inc(); > schedule_hrtimeout(&chill_time, HRTIMER_MODE_REL_HARD); > sleeping_lock_dec(); > if (!freeze_flag) > current->flags &= ~PF_NOFREEZE; > - __set_current_state_no_track(saved_state); > + > + raw_spin_lock_irq(&self->pi_lock); > + __set_current_state_no_track(self->saved_state); > + self->saved_state = TASK_RUNNING; > + raw_spin_unlock_irq(&self->pi_lock); > } > EXPORT_SYMBOL(cpu_chill); > #endif > > Sebastian