Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752855AbdI1MFn (ORCPT ); Thu, 28 Sep 2017 08:05:43 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:41843 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751906AbdI1MFm (ORCPT ); Thu, 28 Sep 2017 08:05:42 -0400 Date: Thu, 28 Sep 2017 14:05:32 +0200 From: Peter Zijlstra To: "Levin, Alexander (Sasha Levin)" Cc: Sergey Senozhatsky , 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 Message-ID: <20170928120532.cjidduvjj5xygaid@hirez.programming.kicks-ass.net> References: <20170928093847.zgcgvxb7ajiaywbr@hirez.programming.kicks-ass.net> <20170928103032.GA2380@jagdpanzerIV.localdomain> <20170928113607.GB30818@jagdpanzerIV.localdomain> <20170928114528.wilknwkyjecqrcaa@sasha-lappy> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170928114528.wilknwkyjecqrcaa@sasha-lappy> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 723 Lines: 17 (please linewrap normal text at 72 chars) On Thu, Sep 28, 2017 at 11:45:30AM +0000, Levin, Alexander (Sasha Levin) wrote: > Okay, that seems to have delt with the callbacks supressed issue. > > I also seem to be hitting it as a result of the scheduler triggering a > WARN, where print_stack_trace(), for example, just uses printk(). > > Now I'm not sure what's your approach here, do we keep converting > printk to printk_deferred one by one until we whacked every mole? Nah.. WARN's _should_ not trigger. If they do we fix that. Getting a lockdep splat after a WARN is something I can live with. And you really don't want that deferred nonsense for WARNs, because that means you'll risk not over getting the output.