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=-1.0 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 8A1BBC43387 for ; Thu, 10 Jan 2019 16:08:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 610F221848 for ; Thu, 10 Jan 2019 16:08:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728687AbfAJQIm (ORCPT ); Thu, 10 Jan 2019 11:08:42 -0500 Received: from mail.kernel.org ([198.145.29.99]:58954 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728213AbfAJQIm (ORCPT ); Thu, 10 Jan 2019 11:08:42 -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 0491A206B7; Thu, 10 Jan 2019 16:08:40 +0000 (UTC) Date: Thu, 10 Jan 2019 11:08:39 -0500 From: Steven Rostedt To: Mathieu Desnoyers Cc: "Paul E. McKenney" , linux-kernel , Peter Zijlstra Subject: Re: Possible use of RCU while in extended QS: idle vs RCU read-side in interrupt vs rcu_eqs_exit Message-ID: <20190110110839.7daeef3d@gandalf.local.home> In-Reply-To: <2103471967.794.1547084331086.JavaMail.zimbra@efficios.com> References: <2103471967.794.1547084331086.JavaMail.zimbra@efficios.com> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 9 Jan 2019 20:38:51 -0500 (EST) Mathieu Desnoyers wrote: > Hi Paul, > > I've had a user report that trace_sched_waking() appears to be > invoked while !rcu_is_watching() in some situation, so I started > digging into the scheduler idle code. I'm wondering if this isn't a bug. Do you have the backtrace for where trace_sched_waking() was called without rcu watching? -- Steve > > It appears that interrupts are re-enabled before rcu_eqs_exit() is > invoked when exiting idle code from the scheduler. > > I wonder what happens if an interrupt handler (including scheduler code) > happens to issue a RCU read-side critical section before rcu_eqs_exit() > is called ? Is there some code on interrupt entry that ensures rcu eqs > state is exited in such scenario ? > > Thanks, > > Mathieu >