From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Jones Subject: Re: lockdep splat in CPU hotplug Date: Tue, 21 Oct 2014 11:10:43 -0400 Message-ID: <20141021151043.GA11800@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Jiri Kosina Cc: Peter Zijlstra , Ingo Molnar , "Rafael J. Wysocki" , Pavel Machek , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org List-Id: linux-pm@vger.kernel.org On Tue, Oct 21, 2014 at 01:09:04PM +0200, Jiri Kosina wrote: > Hi, > > 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. It seems > to imply that cpuidle_pause() is taking cpu_hotplug.lock, but that's not > the case at all. Could inlining be confusing the trace here ? You can get from cpuidle_pause to cpuidle_uninstall_idle_handler -> synchronize_rcu -> synchronize_sched -> synchronize_sched_expedited which does a try_get_online_cpus which will take the cpu_hotplug.lock Dave