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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 C9AF3C433F5 for ; Wed, 29 Aug 2018 08:02:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 67E5A2086D for ; Wed, 29 Aug 2018 08:02:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="K6TbJKu3" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 67E5A2086D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727526AbeH2L6R (ORCPT ); Wed, 29 Aug 2018 07:58:17 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:56952 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726656AbeH2L6R (ORCPT ); Wed, 29 Aug 2018 07:58:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=5S3eaG06txbu1EjRwS19yJixzQzXDZgHsT4vZS72HfE=; b=K6TbJKu3wS3zW0CQeHNR324DD gecm9yTThm2FFvUEV2KF9kSsOeh+EKwTKZtpjYAWyTix77Ni5oyTMrcMsy/Z1vs+xX9P1/luBC+NH tjhH/t8thwQDtXF4mAfYgXg/yki8rtP6XCEDc08OvUBB4imkdIH4BysREXAN21uPWmTusP5nyylAQ 2z3qZ4sIwJFUyBiVmZZRMWN55sPoqDhz+S6yGuyZH++aDoI1FahmDUjpbE1QSLndBOwjK2c0Ya8H0 1GtFrEWgUD2yLReYJGyLTTDcOPEOhViaULg9suItg4rs5z9BnzOvoVfbdAAXupLlwTp3kKhRS051H OT2/NRZxA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fuvQj-0008Sz-Ld; Wed, 29 Aug 2018 08:02:21 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 1D1DD2024EB1E; Wed, 29 Aug 2018 10:02:19 +0200 (CEST) Date: Wed, 29 Aug 2018 10:02:19 +0200 From: Peter Zijlstra To: Srikar Dronamraju Cc: Ingo Molnar , LKML , Mel Gorman , Rik van Riel , Thomas Gleixner , Michael Ellerman , Heiko Carstens , Suravee Suthikulpanit , Andre Wild , linuxppc-dev Subject: Re: [PATCH 2/2] sched/topology: Expose numa_mask set/clear functions to arch Message-ID: <20180829080219.GN24124@hirez.programming.kicks-ass.net> References: <20180808081942.GA37418@linux.vnet.ibm.com> <1533920419-17410-1-git-send-email-srikar@linux.vnet.ibm.com> <1533920419-17410-2-git-send-email-srikar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1533920419-17410-2-git-send-email-srikar@linux.vnet.ibm.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 10, 2018 at 10:30:19PM +0530, Srikar Dronamraju wrote: > With commit 051f3ca02e46 ("sched/topology: Introduce NUMA identity node > sched domain") scheduler introduces an new numa level. However on shared > lpars like powerpc, this extra sched domain creation can lead to > repeated rcu stalls, sometimes even causing unresponsive systems on > boot. On such stalls, it was noticed that init_sched_groups_capacity() > (sg != sd->groups is always true). > > INFO: rcu_sched self-detected stall on CPU > 1-....: (240039 ticks this GP) idle=c32/1/4611686018427387906 softirq=782/782 fqs=80012 > (t=240039 jiffies g=6272 c=6271 q=263040) > NMI backtrace for cpu 1 > --- interrupt: 901 at __bitmap_weight+0x70/0x100 > LR = __bitmap_weight+0x78/0x100 > [c00000832132f9b0] [c0000000009bb738] __func__.61127+0x0/0x20 (unreliable) > [c00000832132fa00] [c00000000016c178] build_sched_domains+0xf98/0x13f0 > [c00000832132fb30] [c00000000016d73c] partition_sched_domains+0x26c/0x440 > [c00000832132fc20] [c0000000001ee284] rebuild_sched_domains_locked+0x64/0x80 > [c00000832132fc50] [c0000000001f11ec] rebuild_sched_domains+0x3c/0x60 > [c00000832132fc80] [c00000000007e1c4] topology_work_fn+0x24/0x40 > [c00000832132fca0] [c000000000126704] process_one_work+0x1a4/0x470 > [c00000832132fd30] [c000000000126a68] worker_thread+0x98/0x540 > [c00000832132fdc0] [c00000000012f078] kthread+0x168/0x1b0 > [c00000832132fe30] [c00000000000b65c] > ret_from_kernel_thread+0x5c/0x80 > > Similar problem was earlier also reported at > https://lwn.net/ml/linux-kernel/20180512100233.GB3738@osiris/ > > Allow arch to set and clear masks corresponding to numa sched domain. What this Changelog fails to do is explain the problem and motivate why this is the right solution. As-is, this reads like, something's buggered, I changed this random thing and it now works. So what is causing that domain construction error?