From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758822AbcJRJZG (ORCPT ); Tue, 18 Oct 2016 05:25:06 -0400 Received: from mail-lf0-f66.google.com ([209.85.215.66]:34728 "EHLO mail-lf0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753191AbcJRJYx (ORCPT ); Tue, 18 Oct 2016 05:24:53 -0400 Date: Tue, 18 Oct 2016 11:24:48 +0200 From: Ingo Molnar To: Wanpeng Li Cc: linux-kernel@vger.kernel.org, Wanpeng Li , Mike Galbraith , Peter Zijlstra , Thomas Gleixner , Paolo Bonzini Subject: Re: [PATCH v2] x86/msr: Add write msr notrace to avoid the debug codes splash Message-ID: <20161018092448.GA28727@gmail.com> References: <1476706603-29346-1-git-send-email-wanpeng.li@hotmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1476706603-29346-1-git-send-email-wanpeng.li@hotmail.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Wanpeng Li wrote: > =============================== > [ INFO: suspicious RCU usage. ] > 4.8.0+ #24 Not tainted > ------------------------------- > ./arch/x86/include/asm/msr-trace.h:47 suspicious rcu_dereference_check() usage! > > other info that might help us debug this: > > RCU used illegally from idle CPU! > rcu_scheduler_active = 1, debug_locks = 0 > RCU used illegally from extended quiescent state! > no locks held by swapper/1/0. > > [] do_trace_write_msr+0x135/0x140 > [] native_write_msr+0x20/0x30 > [] native_apic_msr_eoi_write+0x1d/0x30 > [] smp_reschedule_interrupt+0x1d/0x30 > [] reschedule_interrupt+0x96/0xa0 > > As Peterz pointed out: > > | The thing is, many many smp_reschedule_interrupt() invocations don't > | actually execute anything much at all and are only send to tickle the > | return to user path (which does the actual preemption). > > This patch add write msr notrace to avoid the debug codes splash. > > Suggested-by: Peter Zijlstra > Suggested-by: Paolo Bonzini > Cc: Ingo Molnar > Cc: Mike Galbraith > Cc: Peter Zijlstra > Cc: Thomas Gleixner > Cc: Paolo Bonzini > Signed-off-by: Wanpeng Li > --- > v1 -> v2: > * add write msr notrace to avoid debug codes splash instead of slowdown a very frequent interrupt > > arch/x86/include/asm/apic.h | 4 ++-- > arch/x86/include/asm/msr.h | 15 +++++++++++++++ > arch/x86/kernel/kvm.c | 2 +- > 3 files changed, 18 insertions(+), 3 deletions(-) Could you please do this on top of -tip and also include the revert of: # 1ec6ec14a294 x86/smp: Add irq_enter/exit() in smp_reschedule_interrupt() in your v3 patch, because I'd rather avoid rebasing x86/urgent. Thanks, Ingo