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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 670AAC43387 for ; Mon, 7 Jan 2019 19:54:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 338002183E for ; Mon, 7 Jan 2019 19:54:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728587AbfAGTyc (ORCPT ); Mon, 7 Jan 2019 14:54:32 -0500 Received: from mail.kernel.org ([198.145.29.99]:35466 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728191AbfAGTxf (ORCPT ); Mon, 7 Jan 2019 14:53:35 -0500 Received: from gandalf.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 730CA218C3; Mon, 7 Jan 2019 19:53:34 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.91) (envelope-from ) id 1ggaxp-0000Ll-Ed; Mon, 07 Jan 2019 14:53:33 -0500 Message-Id: <20190107195333.322706801@goodmis.org> User-Agent: quilt/0.65 Date: Mon, 07 Jan 2019 14:53:01 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-rt-users Cc: Thomas Gleixner , Carsten Emde , Sebastian Andrzej Siewior , John Kacur , Paul Gortmaker , Julia Cartwright , Daniel Wagner , tom.zanussi@linux.intel.com, stable-rt@vger.kernel.org, Daniel Bristot de Oliveira Subject: [PATCH RT 09/13] hrtimer: move state change before hrtimer_cancel in do_nanosleep() References: <20190107195252.599921907@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.14.87-rt50-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Sebastian Andrzej Siewior [ Upstream commit 8115ac730fd5aa27134f002cf710204b5dd7cd5e ] There is a small window between setting t->task to NULL and waking the task up (which would set TASK_RUNNING). So the timer would fire, run and set ->task to NULL while the other side/do_nanosleep() wouldn't enter freezable_schedule(). After all we are peemptible here (in do_nanosleep() and on the timer wake up path) and on KVM/virt the virt-CPU might get preempted. So do_nanosleep() wouldn't enter freezable_schedule() but cancel the timer which is still running and wait for it via hrtimer_wait_for_timer(). Then wait_event()/might_sleep() would complain that it is invoked with state != TASK_RUNNING. This isn't a problem since it would be reset to TASK_RUNNING later anyway and we don't rely on the previous state. Move the state update to TASK_RUNNING before hrtimer_cancel() so there are no complains from might_sleep() about wrong state. Cc: stable-rt@vger.kernel.org Reviewed-by: Daniel Bristot de Oliveira Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt (VMware) --- kernel/time/hrtimer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index b59e009087a9..c8d806126381 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -1753,12 +1753,12 @@ static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mod if (likely(t->task)) freezable_schedule(); + __set_current_state(TASK_RUNNING); hrtimer_cancel(&t->timer); mode = HRTIMER_MODE_ABS; } while (t->task && !signal_pending(current)); - __set_current_state(TASK_RUNNING); if (!t->task) return 0; -- 2.19.2