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=-8.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 3EEBEC433E1 for ; Thu, 20 Aug 2020 19:59:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1DFA7207DF for ; Thu, 20 Aug 2020 19:59:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727039AbgHTT71 (ORCPT ); Thu, 20 Aug 2020 15:59:27 -0400 Received: from mail.kernel.org ([198.145.29.99]:46650 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725819AbgHTT70 (ORCPT ); Thu, 20 Aug 2020 15:59:26 -0400 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 3534F2076E; Thu, 20 Aug 2020 19:59:25 +0000 (UTC) Date: Thu, 20 Aug 2020 15:59:23 -0400 From: Steven Rostedt To: Marco Elver Cc: peterz@infradead.org, linux-kernel@vger.kernel.org, mingo@kernel.org, will@kernel.org, npiggin@gmail.com, jgross@suse.com, paulmck@kernel.org, rjw@rjwysocki.net, joel@joelfernandes.org, svens@linux.ibm.com, tglx@linutronix.de Subject: Re: [PATCH 0/9] TRACE_IRQFLAGS wreckage Message-ID: <20200820155923.3d5c4873@oasis.local.home> In-Reply-To: <20200820172046.GA177701@elver.google.com> References: <20200820073031.886217423@infradead.org> <20200820103643.1b9abe88@oasis.local.home> <20200820145821.GA1362448@hirez.programming.kicks-ass.net> <20200820172046.GA177701@elver.google.com> 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 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 20 Aug 2020 19:20:46 +0200 Marco Elver wrote: > On Thu, Aug 20, 2020 at 04:58PM +0200, peterz@infradead.org wrote: > > On Thu, Aug 20, 2020 at 10:36:43AM -0400, Steven Rostedt wrote: > > > > > > I tested this series on top of tip/master and triggered the below > > > warning when running the irqsoff tracer boot up test (config attached). > > > > > > -- Steve > > > > > > Testing tracer irqsoff: > > > > > > ============================= > > > WARNING: suspicious RCU usage > > > 5.9.0-rc1-test+ #92 Not tainted > > > ----------------------------- > > > include/trace/events/lock.h:13 suspicious rcu_dereference_check() usage! > ... > > > > Shiny, I think that wants something like the below, but let me go frob > > my config and test it. > > > > --- > > --- a/drivers/cpuidle/cpuidle.c > > +++ b/drivers/cpuidle/cpuidle.c > ... > > With that applied (manually, due to conflicts), I still get warnings for > certain call locations with KCSAN on (that is with my fix from the other > email): > > | ============================= > | WARNING: suspicious RCU usage > | 5.9.0-rc1+ #23 Tainted: G W > | ----------------------------- > | include/trace/events/random.h:310 suspicious rcu_dereference_check() usage! > | > | other info that might help us debug this: > | > | > | rcu_scheduler_active = 2, debug_locks = 0 > | RCU used illegally from extended quiescent state! > | no locks held by swapper/1/0. > | > | stack backtrace: > | CPU: 1 PID: 0 Comm: swapper/1 Tainted: G W 5.9.0-rc1+ #23 > | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 04/01/2014 > | Call Trace: > | __dump_stack lib/dump_stack.c:77 [inline] > | dump_stack+0xf1/0x14d lib/dump_stack.c:118 > | trace_prandom_u32 include/trace/events/random.h:310 [inline] > | prandom_u32+0x1ee/0x200 lib/random32.c:86 > | prandom_u32_max include/linux/prandom.h:46 [inline] > | reset_kcsan_skip kernel/kcsan/core.c:277 [inline] > | kcsan_setup_watchpoint+0x9b/0x600 kernel/kcsan/core.c:424 > | is_idle_task+0xd/0x20 include/linux/sched.h:1671 <==== inline, but not noinstr > | irqentry_enter+0x17/0x50 kernel/entry/common.c:293 <==== noinstr function > What happens if you apply the below patch? -- Steve diff --git a/lib/random32.c b/lib/random32.c index 932345323af0..1c5607a411d4 100644 --- a/lib/random32.c +++ b/lib/random32.c @@ -83,7 +83,7 @@ u32 prandom_u32(void) u32 res; res = prandom_u32_state(state); - trace_prandom_u32(res); + trace_prandom_u32_rcuidle(res); put_cpu_var(net_rand_state); return res;