Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752867AbdI1LFF (ORCPT ); Thu, 28 Sep 2017 07:05:05 -0400 Received: from omzsmtpe02.verizonbusiness.com ([199.249.25.209]:19208 "EHLO omzsmtpe02.verizonbusiness.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751850AbdI1LFD (ORCPT ); Thu, 28 Sep 2017 07:05:03 -0400 From: "Levin, Alexander (Sasha Levin)" X-Host: challenger.odc.vzwcorp.com To: Peter Zijlstra CC: Sasha Levin , Thomas Gleixner , Ingo Molnar , "linux-kernel@vger.kernel.org List" , "pmladek@suse.com" , "sergey.senozhatsky@gmail.com" , "rostedt@goodmis.org" Subject: Re: sched: serial port lockdep warning when offlining CPUs Thread-Topic: sched: serial port lockdep warning when offlining CPUs Thread-Index: AQHTOEmOtfUEl8arJ0mazitmXnW5SQ== Date: Thu, 28 Sep 2017 11:04:29 +0000 Message-ID: <20170928110428.ew5ukfihb3bdiszr@sasha-lappy> References: <20170928093847.zgcgvxb7ajiaywbr@hirez.programming.kicks-ass.net> In-Reply-To: <20170928093847.zgcgvxb7ajiaywbr@hirez.programming.kicks-ass.net> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: user-agent: NeoMutt/20170113 (1.7.2) x-ms-exchange-messagesentrepresentingtype: 1 x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.144.60.250] Content-Type: text/plain; charset="us-ascii" Content-ID: <3DB84D6DF3CAA940AAA905BC03ED6068@vzwcorp.com> MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id v8SB5BWZ013687 Content-Length: 1636 Lines: 42 On Thu, Sep 28, 2017 at 11:38:47AM +0200, Peter Zijlstra wrote: >On Thu, Sep 28, 2017 at 02:19:46AM -0700, Sasha Levin wrote: >> Hi all, >> >> I seem to be hitting the following warning when offlining CPUs on the >> latest -next kernel: >> >> [289683102.607076] Unregister pv shared memory for cpu 8 >> [289683102.622922] select_fallback_rq: 3 callbacks suppressed > >This is because you hit a printk() from the scheduler, that's known >broken (along with the rest of printk). > >You forgot to actually include that printk() though I suspect it reads >like: > > "process %d (%s) no longer affine to cpu%d\n" > >Now that uses printk_deferred() which _should_ work lots better, but >clearly the printk() stuff went wobbly again. Hm, so is this an actual possible lockup, or just a false positive? >> [289683102.626292] vprintk_emit (kernel/printk/printk.c:1876) >> [289683102.626294] vprintk_default (kernel/printk/printk.c:1918) >> [289683102.626295] vprintk_func (kernel/printk/printk_safe.c:382) >> [289683102.626297] printk (kernel/printk/printk.c:1943) >> [289683102.626299] ? show_regs_print_info (kernel/printk/printk.c:1943) >> [289683102.626301] ? lock_acquire (kernel/locking/lockdep.c:4004) >> [289683102.626306] ___ratelimit (lib/ratelimit.c:52) >> [289683102.626309] __printk_ratelimit (kernel/printk/printk.c:2874) >> [289683102.626311] select_fallback_rq (kernel/sched/core.c:1525 (discriminator 1)) >> [289683102.626313] sched_cpu_dying (kernel/sched/core.c:5500 kernel/sched/core.c:5687) > >Also, could you pretty please not line wrap logs? Sure, I had to resort to using gmail at a conference :( -- Thanks, Sasha