Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933699AbbHLLAa (ORCPT ); Wed, 12 Aug 2015 07:00:30 -0400 Received: from mail-wi0-f176.google.com ([209.85.212.176]:33735 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754588AbbHLLA2 (ORCPT ); Wed, 12 Aug 2015 07:00:28 -0400 Date: Wed, 12 Aug 2015 12:00:25 +0100 From: Matt Fleming To: Yasuaki Ishimatsu Cc: peterz@infradead.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, vikas.shivappa@intel.com, kanaka.d.juvva@intel.com, matt.fleming@intel.com Subject: Re: [PATCH] perf/x86/intel/cqm: Move WARN_ONs from intel_cqm_cpu_prepare to cqm_pick_event_reader Message-ID: <20150812110025.GA2922@codeblueprint.co.uk> References: <55ca5b89.210f370a.78441.ffffa014@mx.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55ca5b89.210f370a.78441.ffffa014@mx.google.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4049 Lines: 79 On Tue, 11 Aug, at 01:31:05PM, Yasuaki Ishimatsu wrote: > When hot adding a CPU and onlining it, the following WARN_ON() messages > are shown: > > [ 772.891448] ------------[ cut here ]------------ > [ 772.896624] WARNING: CPU: 58 PID: 15169 at arch/x86/kernel/cpu/perf_event_intel_cqm.c:1268 intel_cqm_cpu_prepare+0x88/0x90() > [ 772.909167] Modules linked in: > [ 772.995134] CPU: 58 PID: 15169 > [ 773.016633] 0000000000000000 0000000092fb60ed ffff88104febbba8 ffffffff8167b5fa > [ 773.024789] 0000000000000000 0000000000000000 ffff88104febbbe8 ffffffff810819ea > [ 773.033119] ffff88103be60000 ffff8c0fbc7ca020 ffffffff819fadf0 000000000000008f > [ 773.041461] Call Trace: > [ 773.044402] [] dump_stack+0x45/0x57 > [ 773.050160] [] warn_slowpath_common+0x8a/0xc0 > [ 773.056888] [] warn_slowpath_null+0x1a/0x20 > [ 773.063426] [] intel_cqm_cpu_prepare+0x88/0x90 > [ 773.070253] [] intel_cqm_cpu_notifier+0x42/0x160 > [ 773.077271] [] notifier_call_chain+0x4d/0x80 > [ 773.083901] [] __raw_notifier_call_chain+0xe/0x10 > [ 773.091007] [] _cpu_up+0xe8/0x190 > [ 773.096555] [] cpu_up+0x7a/0xa0 > [ 773.101910] [] cpu_subsys_online+0x40/0x90 > [ 773.108332] [] device_online+0x67/0x90 > [ 773.114368] [] online_store+0x8a/0xa0 > [ 773.120305] [] dev_attr_store+0x18/0x30 > [ 773.126437] [] sysfs_kf_write+0x3a/0x50 > [ 773.132560] [] kernfs_fop_write+0x120/0x170 > [ 773.139078] [] __vfs_write+0x37/0x100 > [ 773.145019] [] ? __sb_start_write+0x58/0x110 > [ 773.151635] [] ? security_file_permission+0x3d/0xc0 > [ 773.158932] [] vfs_write+0xa9/0x190 > [ 773.164674] [] ? do_audit_syscall_entry+0x66/0x70 > [ 773.171776] [] SyS_write+0x55/0xc0 > [ 773.177423] [] ? do_page_fault+0x30/0x80 > [ 773.183654] [] entry_SYSCALL_64_fastpath+0x12/0x71 > [ 773.190843] ---[ end trace e6219d24386873bd ]--- > [ 773.196573] smpboot: Booting Node 7 Processor 143 APIC 0x1f7 > [ 773.221241] microcode: CPU143 sig=0x306f3, pf=0x80, revision=0x9 > [ 773.228005] Will online and init hotplugged CPU: 143 > > Here is the root cause of the issue: > When calling intel_cqm_cpu_prepare() at CPU_UP_PREPARE notification, > the function checks that c86_chache_max_rmid is same as cqm_max_rmid > as follows: > > static void intel_cqm_cpu_prepare(unsigned int cpu) > { > ... > WARN_ON(c->x86_cache_max_rmid != cqm_max_rmid); > > But x86_cache_max_rmid of hot added CPU is not set yet, because it will > set in get_cpu_cap() which is called after CPU_UP_PREPARE notification. > > So when onlining a hot added CPU, the WARN_ON() are always shown: Thanks for the report! I submitted the following patch on August 6th to fix this issue, https://lkml.kernel.org/r/1438863163-14083-1-git-send-email-matt@codeblueprint.co.uk > To fix the issue, the patch moves WARN_ON()s from intel_cqm_cpu_prepare() to > cqm_pick_event_reader() which is called at CPU_STARTING notification. I took a different approach and moved the notifier from CPU_UP_PREPARE to CPU_STARTING since there's no reason to call the handler as early as CPU_UP_PREPARE time at all. Yes, we could collapse cqm_pick_event_reader() and intel_cqm_cpu_prepare() together but I have a patch to add a CPU_DOWN_FAILED call that invokes cqm_pick_event_reader() but not intel_cqm_cpu_prepare(). I actually need to mail that out. -- Matt Fleming, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/