From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E346FC432C3 for ; Tue, 3 Dec 2019 15:57:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B7ADC205ED for ; Tue, 3 Dec 2019 15:57:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726452AbfLCP5F convert rfc822-to-8bit (ORCPT ); Tue, 3 Dec 2019 10:57:05 -0500 Received: from esa2.mentor.iphmx.com ([68.232.141.98]:32314 "EHLO esa2.mentor.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726024AbfLCP5F (ORCPT ); Tue, 3 Dec 2019 10:57:05 -0500 IronPort-SDR: VxIQnOTTdlXd9liSPgcQK4Whyx+1NIppr0A3wHI5WoX7I7PM5yV6yk6SCqceLt7ygC/eZp5RdU 3igOzQ+YnnDs2QNVsxcadO3eiPTyJzuD2FLLw7BttT6G5PmRzt9x70GnR7pQvWaWdmPv08ylJQ 5xE9iZt5HpPLw21Rm8AEvP+2Oh5WFHAuywNy9c7/F/oa3XzBYufKrHoU3Qg/aaidJ+bApL9bvc +zerpKsMC9kJA+SlWMzZ8Bcu3iPXvZJXA6b6/CzpbgOCCO/Hl72lNM+yJkW5+edRT35pVMQlll ZYY= X-IronPort-AV: E=Sophos;i="5.69,273,1571731200"; d="scan'208";a="43664870" Received: from orw-gwy-01-in.mentorg.com ([192.94.38.165]) by esa2.mentor.iphmx.com with ESMTP; 03 Dec 2019 07:57:04 -0800 IronPort-SDR: c1ll72oAVbrRtpN2MlMAv85kuHIg3Pr27RPIejF7/YT9Xhbihy7FV7ZULzNIJVc70ueP+dXMt3 Qo9PGeJF0/sfI8kQW9J1WGAVQT10rQ47zKyNwyUsdKC+sJuzDQZnLI7U8ZjBTGy254lfwyIjBG /kJ8C8cEpFspjfpTtDhVJnWLgS99uuRf6NjJwL/LuWdE/Nd4se3czy6Cp842rA0u9/mfCA1CB2 DSBhMhcSd73GZev26ztxqSIR8HgVLFie0sVs4LChY4VNTBQ2Oi9GWkIwpYrvlRo0J2iTgmNRW3 RW0= From: "Schmid, Carsten" To: Dietmar Eggemann , Valentin Schneider , "mingo@redhat.com" , "peterz@infradead.org" , "linux-kernel@vger.kernel.org" Subject: AW: Crash in fair scheduler Thread-Topic: Crash in fair scheduler Thread-Index: AQHVqbfg64Wqju89WkedWbWijDxswKeoNeoAgAACxACAAAgggIAAQtOAgAAMFgA= Date: Tue, 3 Dec 2019 15:57:00 +0000 Message-ID: References: <1575364273836.74450@mentor.com> <564e45cb-8230-9c3d-24a8-b58e6e88349f@arm.com> <944927a7-b578-c6f9-a73d-25c5b0a39adb@arm.com> In-Reply-To: Accept-Language: de-DE, en-IE, en-US Content-Language: de-DE X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [137.202.0.90] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On 03/12/2019 12:09, Valentin Schneider wrote: > > On 03/12/2019 10:40, Dietmar Eggemann wrote: > >> On 03/12/2019 11:30, Valentin Schneider wrote: > >>> On 03/12/2019 09:11, Schmid, Carsten wrote: > >> > >> [...] > > I can't reproduce it on Arm64 Juno running 4.14.86. I suppose that there > is no extra reproducer testcase since the issue happened with > prev->sched_class eq. &idle_sched_class [prev eq. swapper/X 0] in the > simple path of pick_next_task_fair(). > > I'm running with CONFIG_SCHED_AUTOGROUP=y and > CONFIG_FAIR_GROUP_SCHED=y > some taskgroup related tests for hours now. So the sched_entity (se) can > be a task, an autogroup or a taskgroup in the simple path. pref is > either swapper/X or migration/X. We have the same kernel config settings. However, as i stated in the analysis, we had prev->sched_class ne. &fair_sched_class and, unfortunately, no reproducer. Looks like we need to find out why rb_leftmost is 0x0/NULL.