From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751791AbbHBQDN (ORCPT ); Sun, 2 Aug 2015 12:03:13 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:49898 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751456AbbHBQDM (ORCPT ); Sun, 2 Aug 2015 12:03:12 -0400 Date: Sun, 2 Aug 2015 18:03:01 +0200 From: Peter Zijlstra To: Dave Jones , Linux Kernel , "Paul E. McKenney" , Josh Triplett Subject: Re: unpinning an unpinned lock. (pidns/scheduler) Message-ID: <20150802160301.GE25159@twins.programming.kicks-ass.net> References: <20150731174353.GA25799@codemonkey.org.uk> <20150802153807.GA1572@codemonkey.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150802153807.GA1572@codemonkey.org.uk> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Aug 02, 2015 at 11:38:07AM -0400, Dave Jones wrote: > On Fri, Jul 31, 2015 at 01:43:53PM -0400, Dave Jones wrote: > > Just found a machine with this on 4.2-rc4 > > > > WARNING: CPU: 0 PID: 11787 at kernel/locking/lockdep.c:3497 lock_unpin_lock+0x109/0x110() > > unpinning an unpinned lock > > CPU: 0 PID: 11787 Comm: kworker/0:1 Not tainted 4.2.0-rc4-think+ #5 > > Workqueue: events proc_cleanup_work > > 0000000000000009 ffff8804f8983988 ffffffff9f7f5eed 0000000000000007 > > ffff8804f89839d8 ffff8804f89839c8 ffffffff9f07b72a 00000000000000a8 > > 0000000000000070 ffff8805079d5c98 0000000000000092 0000000000000002 > > Call Trace: > > [] dump_stack+0x4f/0x7b > > [] warn_slowpath_common+0x8a/0xc0 > > [] warn_slowpath_fmt+0x46/0x50 > > [] lock_unpin_lock+0x109/0x110 > > [] __schedule+0x39f/0xb30 > > [] schedule+0x41/0x90 > > ---[ end trace e75342db87128aeb ]--- > > I'm hitting this a few times a day now, I'll see if I can narrow down > a reproducer next week. Adding the RCU cabal to Cc. Thanks, I got a report from Sasha as well, but so far I'm a bit stumped on how this can happen. Clearly there's an imbalance in some unlikely scheduler path, but so far its eluding me :/