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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 46A9EC433E0 for ; Sat, 6 Jun 2020 17:29:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 210B62077D for ; Sat, 6 Jun 2020 17:29:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591464586; bh=InFdTWf+AQ3EEuNVLEAMS/IifpeSAsaN4CaqB7gUAzk=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=ivB+xpMkXX8VJdtR/JrVA6Rqc25EqRVCsBYb53phXFHCoP03WnQn9pBn6Ws/kUmcB edE9VJvANYgxDwmjyMWZnhbcmxaEb9fGVsIBy6rOvJus1LdcLv1qQuHBShGuHQK9zO hKRax7gaXgUZFc6T5Di5nI2E9gvOGPx/i+YWYzWo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728768AbgFFR3n (ORCPT ); Sat, 6 Jun 2020 13:29:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:44566 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727906AbgFFR3m (ORCPT ); Sat, 6 Jun 2020 13:29:42 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (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 4AA632073E; Sat, 6 Jun 2020 17:29:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591464582; bh=InFdTWf+AQ3EEuNVLEAMS/IifpeSAsaN4CaqB7gUAzk=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=GiJAvw09oFkrMoCXInmQ6jKjBSjNEMyqu4+3zWeDhgsq3R8kVbSyprV8OaKxR3kQ9 cUmhveo68DnzuNxdNGDFO08Sr+8GtjwglGcYaQQNqKGTM7uMX3Rpgc+pXN8R/DPTuj V64CNmVgW1ulp4BEKFkczum3vkH5XCCcW8NNXGQQ= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 1A0A935209C2; Sat, 6 Jun 2020 10:29:42 -0700 (PDT) Date: Sat, 6 Jun 2020 10:29:42 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: Re: BUG: kernel NULL pointer dereference from check_preempt_wakeup() Message-ID: <20200606172942.GA30594@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200604225445.GA32319@paulmck-ThinkPad-P72> <20200605131451.GE2750@hirez.programming.kicks-ass.net> <20200605141607.GB4455@paulmck-ThinkPad-P72> <20200605184159.GA4062@paulmck-ThinkPad-P72> <20200606005126.GA21507@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200606005126.GA21507@paulmck-ThinkPad-P72> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 05, 2020 at 05:51:26PM -0700, Paul E. McKenney wrote: > On Fri, Jun 05, 2020 at 11:41:59AM -0700, Paul E. McKenney wrote: > > On Fri, Jun 05, 2020 at 07:16:07AM -0700, Paul E. McKenney wrote: > > > On Fri, Jun 05, 2020 at 03:14:51PM +0200, Peter Zijlstra wrote: > > > > > > No KCSAN. GCC 8.2.1. No cgroups unless the kernel creates some. > > > No userspace other than a C-language binary named "init" that > > > sleeps in an infinite loop. > > > > > > .config attached. > > > > And in case it is helpful, here is the output of "git bisect view", > > which lists rather more commits than "git bisect run" claims, but there > > are only a few scheduler commits below. I don't see anything that > > I can prove can cause this problem, but there are some that are at > > least related to this code path. > > > > Is there anything that is actually relevant? > > And the run with the WARN and tracing did hit two failures, and the > corresponding console logs are in the attached tarball. Both of them > triggered a warning as well as the failure. And the current state of the bisection, for whatever it is worth. Thanx, Paul ------------------------------------------------------------------------ dbe9337109c2 sched/cpuacct: Fix charge cpuacct.usage_sys 04f5c362ec6d sched/fair: Replace zero-length array with flexible-array 95d685935a2e sched/pelt: Sync util/runnable_sum with PELT window when propagating 12aa2587388d sched/cpuacct: Use __this_cpu_add() instead of this_cpu_ptr() 7d148be69e3a sched/fair: Optimize enqueue_task_fair() 9013196a467e Merge branch 'sched/urgent' 2a0a24ebb499 sched: Make scheduler_ipi inline 90b5363acd47 sched: Clean up scheduler_ipi() b1d1779e5ef7 sched/core: Simplify sched_init() 12ac6782a40a sched/swait: Reword some of the main description 17c891ab3491 sched/fair: Use __this_cpu_read() in wake_wide() bf2c59fce407 sched/core: Fix illegal RCU from offline CPUs f38f12d1e081 sched/fair: Mark sched_init_granularity __init 5a6d6a6ccb5f sched/fair: Refill bandwidth before scaling 457d1f465778 sched: Extract the task putting code from pick_next_task() d91cecc15662 sched: Make newidle_balance() static again 36c5bdc43870 sched/topology: Kill SD_LOAD_BALANCE e669ac8ab952 sched: Remove checks against SD_LOAD_BALANCE 9818427c6270 sched/debug: Make sd->flags sysctl read-only 45da27732b0b sched/fair: find_idlest_group(): Remove unused sd_flag parameter 586b58cac8b4 exit: Move preemption fixup up, move blocking operations down 64297f2b03cc sched/fair: Simplify the code of should_we_balance() ab93a4bc955b sched/fair: Remove distribute_running from CFS bandwidth e98fa02c4f2e sched/fair: Eliminate bandwidth race between throttling and distribution f080d93e1d41 sched/debug: Fix trival print_task() format