Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752367AbdHCD4a (ORCPT ); Wed, 2 Aug 2017 23:56:30 -0400 Received: from mail-pg0-f43.google.com ([74.125.83.43]:34819 "EHLO mail-pg0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752347AbdHCD42 (ORCPT ); Wed, 2 Aug 2017 23:56:28 -0400 Subject: Re: rcu_sched stall while waiting in csd_lock_wait() To: Marc Zyngier , Will Deacon Cc: linux-arm-kernel , open list , Peter Zijlstra , "Paul E. McKenney" , mark.rutland@arm.com References: <20170802080827.GA15219@arm.com> From: Pratyush Anand Message-ID: <29ea458d-f415-4913-8b54-db5c334ce829@redhat.com> Date: Thu, 3 Aug 2017 09:26:24 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1097 Lines: 29 Hi Marc, On Wednesday 02 August 2017 02:14 PM, Marc Zyngier wrote: > On 02/08/17 09:08, Will Deacon wrote: >> Hi Pratyush, >> >> On Wed, Aug 02, 2017 at 09:01:19AM +0530, Pratyush Anand wrote: >>> I am observing following rcu_sched stall while executing `perf record -a -- >>> sleep 1` with one of the arm64 platform. It looks like that stalled cpu was >>> waiting in csd_lock_wait() from where it never came out,and so the stall. >>> Any help/pointer for further debugging would be very helpful. Problem also >>> reproduced with 4.13.0-rc3. >> >> When you say "also", which other kernel(s) show the problem? Is this a >> recent regression? Which platform are you running on? >> >> It would be interesting to know what the other CPUs are doing, in particular >> the target of the cross-call. Either it crashed spectacularly and didn't >> unlock the csd lock, or the IPI somehow wasn't delivered. >> >> Do you see any other splats if you enable lock debugging? > > Also, is that in a guest, or bare metal? If that's a guest, what's the > host's kernel version? Its a host. -- Regards Pratyush