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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 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 54543C56202 for ; Tue, 24 Nov 2020 20:32:54 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8F402206E0 for ; Tue, 24 Nov 2020 20:32:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8F402206E0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id AC7546B006E; Tue, 24 Nov 2020 15:32:52 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A78516B0070; Tue, 24 Nov 2020 15:32:52 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 98EAB6B0071; Tue, 24 Nov 2020 15:32:52 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0028.hostedemail.com [216.40.44.28]) by kanga.kvack.org (Postfix) with ESMTP id 854C16B006E for ; Tue, 24 Nov 2020 15:32:52 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 54FA2180AD801 for ; Tue, 24 Nov 2020 20:32:52 +0000 (UTC) X-FDA: 77520460584.27.soda70_2a0653c27370 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin27.hostedemail.com (Postfix) with ESMTP id 343703D663 for ; Tue, 24 Nov 2020 20:32:52 +0000 (UTC) X-HE-Tag: soda70_2a0653c27370 X-Filterd-Recvd-Size: 2803 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf16.hostedemail.com (Postfix) with ESMTP for ; Tue, 24 Nov 2020 20:32:51 +0000 (UTC) Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (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 C409620678; Tue, 24 Nov 2020 20:32:47 +0000 (UTC) Date: Tue, 24 Nov 2020 15:32:45 -0500 From: Steven Rostedt To: Mark Rutland Cc: "Paul E. McKenney" , Marco Elver , Will Deacon , Anders Roxell , Andrew Morton , Alexander Potapenko , Dmitry Vyukov , Jann Horn , Linux Kernel Mailing List , Linux-MM , kasan-dev , rcu@vger.kernel.org, Peter Zijlstra , Tejun Heo , Lai Jiangshan , linux-arm-kernel@lists.infradead.org, boqun.feng@gmail.com, tglx@linutronix.de Subject: Re: linux-next: stall warnings and deadlock on Arm64 (was: [PATCH] kfence: Avoid stalling...) Message-ID: <20201124153245.5bda420d@oasis.local.home> In-Reply-To: <20201124194308.GC8957@C02TD0UTHF1T.local> References: <20201119170259.GA2134472@elver.google.com> <20201119184854.GY1437@paulmck-ThinkPad-P72> <20201119193819.GA2601289@elver.google.com> <20201119213512.GB1437@paulmck-ThinkPad-P72> <20201119225352.GA5251@willie-the-truck> <20201120103031.GB2328@C02TD0UTHF1T.local> <20201120140332.GA3120165@elver.google.com> <20201123193241.GA45639@C02TD0UTHF1T.local> <20201124140310.GA811510@elver.google.com> <20201124150146.GH1437@paulmck-ThinkPad-P72> <20201124194308.GC8957@C02TD0UTHF1T.local> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 Tue, 24 Nov 2020 19:43:08 +0000 Mark Rutland wrote: > AFAICT, the issue is that arch_cpu_idle() can be dynamically traced with > ftrace, and hence the tracing code can unexpectedly run without RCU > watching. Since that's dynamic tracing, we can avoid it by marking > arch_cpu_idle() and friends as noinstr. Technically, ftrace doesn't care if RCU is watching or not, but the callbacks might, and they need to do the rcu_is_watching() check if they do. Although, there's work to keep those areas from being traced, but to do so, they really need to be minimal, where you don't ever want to trace them. -- Steve