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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 17911C636CA for ; Sun, 18 Jul 2021 22:52:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F16AA610C7 for ; Sun, 18 Jul 2021 22:52:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233530AbhGRWza (ORCPT ); Sun, 18 Jul 2021 18:55:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47844 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231846AbhGRWz3 (ORCPT ); Sun, 18 Jul 2021 18:55:29 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CCF2BC061762; Sun, 18 Jul 2021 15:52:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=RHSK5EGB6FHr3oxPvJZpzufbw3Ms9NA52kVasTcg4p4=; b=EO8B14wpWTQwqTdTHNRIsPGLqT wOvfRyDsX9UOviGYwZ6BLIZSOb8CNAH48qsNPi0CRJ6xSG9tFMXwvUCP3tM3OEK2nQvhOArtaBSfE bXaA5NbN5MMB/fpIg1U7PR4ROUcddLqQa5S9BKCm0ibaKVzDluRcku6kRN5Dk+pF2ksqzAFAAxU2b H/FePW411Q6kY2HM9g8JIVC6oD3kfulR9lETb8rwxMswGtNvjxDxFWTWyASrLxZi0KZjN4m0B9LPf 6P7FfzVWDYjvBOlG/ZWNOFdyMVJDTz0tx0KYghGMOprXcwYI96BFG97OYG17pLT87GvlOJ09Ko38/ WlThaU3w==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1m5FdI-006MEM-As; Sun, 18 Jul 2021 22:51:56 +0000 Date: Sun, 18 Jul 2021 23:51:36 +0100 From: Matthew Wilcox To: "Paul E. McKenney" Cc: Oleksandr Natalenko , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Chris Clayton , Chris Rankin , Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , rcu@vger.kernel.org, Andrew Morton , linux-mm@kvack.org Subject: Re: linux-5.13.2: warning from kernel/rcu/tree_plugin.h:359 Message-ID: References: <2245518.LNIG0phfVR@natalenko.name> <6698965.kvI7vG0SvZ@natalenko.name> <20210718215914.GQ4397@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210718215914.GQ4397@paulmck-ThinkPad-P17-Gen-1> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Sun, Jul 18, 2021 at 02:59:14PM -0700, Paul E. McKenney wrote: > > > https://lore.kernel.org/lkml/CAK2bqVK0Q9YcpakE7_Rc6nr-E4e2GnMOgi5jJj=_Eh_1k > > > EHLHA@mail.gmail.com/ > > But this one does show this warning in v5.12.17: > > WARN_ON_ONCE(!preempt && rcu_preempt_depth() > 0); > > This is in rcu_note_context_switch(), and could be caused by something > like a schedule() within an RCU read-side critical section. This would > of course be RCU-usage bugs, given that you are not permitted to block > within an RCU read-side critical section. > > I suggest checking the functions in the stack trace to see where the > rcu_read_lock() is hiding. CONFIG_PROVE_LOCKING might also be helpful. I'm not sure I see it in this stack trace. Is it possible that there's something taking the rcu read lock in an interrupt handler, then returning from the interrupt handler without releasing the rcu lock? Do we have debugging that would fire if somebody did this?