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=-3.8 required=3.0 tests=BAYES_00, 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 EAB6AC5519F for ; Wed, 25 Nov 2020 10:29:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AC77F20857 for ; Wed, 25 Nov 2020 10:29:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727663AbgKYK3E (ORCPT ); Wed, 25 Nov 2020 05:29:04 -0500 Received: from foss.arm.com ([217.140.110.172]:38578 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725838AbgKYK3D (ORCPT ); Wed, 25 Nov 2020 05:29:03 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9AE40106F; Wed, 25 Nov 2020 02:29:02 -0800 (PST) Received: from C02TD0UTHF1T.local (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BDFA93F70D; Wed, 25 Nov 2020 02:28:59 -0800 (PST) Date: Wed, 25 Nov 2020 10:28:49 +0000 From: Mark Rutland To: Marco Elver Cc: Will Deacon , "Paul E. McKenney" , Steven Rostedt , 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: <20201125102849.GB70906@C02TD0UTHF1T.local> References: <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> <20201124193034.GB8957@C02TD0UTHF1T.local> <20201125094517.GA1359135@elver.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201125094517.GA1359135@elver.google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 25, 2020 at 10:45:17AM +0100, Marco Elver wrote: > On Tue, Nov 24, 2020 at 07:30PM +0000, Mark Rutland wrote: [...] > > > I noticed there are a bunch of warnings in the log > > > that might be relevant (see attached). > > > > > [ 91.184432] ============================= > > > [ 91.188301] WARNING: suspicious RCU usage > > > [ 91.192316] 5.10.0-rc4-next-20201119-00002-g51c2bf0ac853 #25 Tainted: G W > > > [ 91.197536] ----------------------------- > > > [ 91.201431] kernel/trace/trace_preemptirq.c:78 RCU not watching trace_hardirqs_off()! > > > [ 91.206546] > > > [ 91.206546] other info that might help us debug this: > > > [ 91.206546] > > > [ 91.211790] > > > [ 91.211790] rcu_scheduler_active = 2, debug_locks = 0 > > > [ 91.216454] RCU used illegally from extended quiescent state! > > > [ 91.220890] no locks held by swapper/0/0. > > > [ 91.224712] > > > [ 91.224712] stack backtrace: > > > [ 91.228794] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W 5.10.0-rc4-next-20201119-00002-g51c2bf0ac853 #25 > > > [ 91.234877] Hardware name: linux,dummy-virt (DT) > > > [ 91.239032] Call trace: > > > [ 91.242587] dump_backtrace+0x0/0x240 > > > [ 91.246500] show_stack+0x34/0x88 > > > [ 91.250295] dump_stack+0x140/0x1bc > > > [ 91.254159] lockdep_rcu_suspicious+0xe4/0xf8 > > > [ 91.258332] trace_hardirqs_off+0x214/0x330 > > > [ 91.262462] trace_graph_return+0x1ac/0x1d8 > > > [ 91.266564] ftrace_return_to_handler+0xa4/0x170 > > > [ 91.270809] return_to_handler+0x1c/0x38 > > > [ 91.274826] default_idle_call+0x94/0x38c > > > [ 91.278869] do_idle+0x240/0x290 > > > [ 91.282633] rest_init+0x1e8/0x2dc > > > [ 91.286529] arch_call_rest_init+0x1c/0x28 > > > [ 91.290585] start_kernel+0x638/0x670 > > > > Hmm... I suspect that arch_cpu_idle() is being traced here, and I reckon > > we have to mark that and its callees as noinstr, since it doesn't seem > > sane to have ftrace check whether RCU is watching for every function > > call. Maybe Paul or Steve can correct me. ;) > > Yes, it's arch_cpu_idle(). > > > If you still have the binary lying around, can you check whether > > default_idle_call+0x94/0x38c is just after the call to arch_cpu_idle()? > > If you could dump the asm around that, along with whatever faddr2line > > tells you, that'd be a great help. > > I reran to be sure, with similar results. I've attached a > syz-symbolize'd version of the warnings. Thanks for confirming, and for the symbolized report. I'll see about getting this fixed ASAP. Thanks, Mark.