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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 6B29BC636C8 for ; Sun, 18 Jul 2021 22:53:31 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D16B56101E for ; Sun, 18 Jul 2021 22:53:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D16B56101E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 154998D00FC; Sun, 18 Jul 2021 18:53:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1062B8D00FA; Sun, 18 Jul 2021 18:53:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F0F198D00FC; Sun, 18 Jul 2021 18:53:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0234.hostedemail.com [216.40.44.234]) by kanga.kvack.org (Postfix) with ESMTP id CDA898D00FA for ; Sun, 18 Jul 2021 18:53:30 -0400 (EDT) Received: from smtpin32.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 5ECF422AC2 for ; Sun, 18 Jul 2021 22:53:29 +0000 (UTC) X-FDA: 78377211738.32.39BF29C Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf13.hostedemail.com (Postfix) with ESMTP id ABD291008622 for ; Sun, 18 Jul 2021 22:53:28 +0000 (UTC) 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> Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=EO8B14wp; spf=none (imf13.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none X-Rspamd-Server: rspam02 X-Stat-Signature: 7fcz1ditc374d5de5wnyijq3mrbs7soe X-Rspamd-Queue-Id: ABD291008622 X-HE-Tag: 1626648808-773081 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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?