From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Lezcano Subject: Re: lockdep splat in CPU hotplug Date: Wed, 22 Oct 2014 16:45:01 +0200 Message-ID: <5447C2ED.5020707@linaro.org> References: <5447BEFE.2040806@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-wg0-f50.google.com ([74.125.82.50]:37577 "EHLO mail-wg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751386AbaJVOpG (ORCPT ); Wed, 22 Oct 2014 10:45:06 -0400 Received: by mail-wg0-f50.google.com with SMTP id a1so3928730wgh.33 for ; Wed, 22 Oct 2014 07:45:04 -0700 (PDT) In-Reply-To: Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Jiri Kosina Cc: Peter Zijlstra , Ingo Molnar , "Rafael J. Wysocki" , Pavel Machek , Steven Rostedt , Dave Jones , "Paul E. McKenney" , Nicolas Pitre , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org On 10/22/2014 04:36 PM, Jiri Kosina wrote: > On Wed, 22 Oct 2014, Daniel Lezcano wrote: > >>>> I am seeing the lockdep report below when resuming from suspend-to= -disk >>>> with current Linus' tree (c2661b80609). >>>> >>>> The reason for CCing Ingo and Peter is that I can't make any sense= of one >>>> of the stacktraces lockdep is providing. >>>> >>>> Please have a look at the very first stacktrace in the dump, where= lockdep >>>> is trying to explain where cpu_hotplug.lock#2 has been acquired. I= t seems >>>> to imply that cpuidle_pause() is taking cpu_hotplug.lock, but that= 's not >>>> the case at all. >>>> >>>> What am I missing? >>> >>> Okay, reverting 442bf3aaf55a ("sched: Let the scheduler see CPU idl= e >>> states") and followup 83a0a96a5f26 ("sched/fair: Leverage the idle = state >>> info when choosing the "idlest" cpu") which depends on it makes the= splat >>> go away. >> >> Are you able to reproduce it by offlining the cpu and onlining it ag= ain ? > > No, that doesn't trigger it (please note that all the relevant stackt= races > from lockdep are going through hibernation). Ok, thanks. --=20 Linaro.org =E2=94=82 Open source software fo= r ARM SoCs =46ollow Linaro: Facebook | Twitter | Blog