From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751512Ab2GSNce (ORCPT ); Thu, 19 Jul 2012 09:32:34 -0400 Received: from mail.skyhub.de ([78.46.96.112]:44263 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751064Ab2GSNca (ORCPT ); Thu, 19 Jul 2012 09:32:30 -0400 Date: Thu, 19 Jul 2012 15:32:29 +0200 From: Borislav Petkov To: "Srivatsa S. Bhat" Cc: msb@chromium.org, mingo@kernel.org, linux-kernel@vger.kernel.org, shaohua.li@intel.com, yinghai@kernel.org, tglx@linutronix.de, hpa@zytor.com, x86@kernel.org, tj@kernel.org, akpm@linux-foundation.org, sfr@canb.auug.org.au, cl@gentwo.org, olofj@chromium.org, paulmck@linux.vnet.ibm.com, Alex Shi , Conny Seidel Subject: Re: [PATCH] x86, mm: Send tlb flush IPIs to online cpus only Message-ID: <20120719133229.GB10073@x1.osrc.amd.com> Mail-Followup-To: Borislav Petkov , "Srivatsa S. Bhat" , msb@chromium.org, mingo@kernel.org, linux-kernel@vger.kernel.org, shaohua.li@intel.com, yinghai@kernel.org, tglx@linutronix.de, hpa@zytor.com, x86@kernel.org, tj@kernel.org, akpm@linux-foundation.org, sfr@canb.auug.org.au, cl@gentwo.org, olofj@chromium.org, paulmck@linux.vnet.ibm.com, Alex Shi , Conny Seidel References: <20120719125643.30033.58913.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20120719125643.30033.58913.stgit@srivatsabhat.in.ibm.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 On Thu, Jul 19, 2012 at 06:27:33PM +0530, Srivatsa S. Bhat wrote: [ … ] > So we are sending an IPI to a cpu which is now offline. Once a cpu is offline, > it will no longer respond to IPIs. This explains the softlockup. > > A cpu in the mm_cpumask could go offline before we send the invalidate > IPI causing us to wait forever. Avoid this by sending the IPI to only the > online cpus. > > [Since flush_tlb_others_ipi() is always called with preempt disabled, it is > not possible for a CPU to go offline once we enter this function, because > CPU offline goes through the stop_machine() stuff (which cannot proceed until > all preempt disabled sections are exited). So we don't have to worry about > any race between CPU offline and the target cpumask calculation in > flush_tlb_others_ipi().] > > Addresses http://crosbug.com/31737 > > Reported-and-debugged-by: Mandeep Singh Baines > Signed-off-by: Srivatsa S. Bhat > Acked-by: Mandeep Singh Baines > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: "H. Peter Anvin" > Cc: x86@kernel.org > Cc: Tejun Heo > Cc: Andrew Morton > Cc: Stephen Rothwell > Cc: Christoph Lameter > Cc: Olof Johansson > --- > > arch/x86/mm/tlb.c | 6 +++++- > 1 files changed, 5 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c > index 5e57e11..9d387a9 100644 > --- a/arch/x86/mm/tlb.c > +++ b/arch/x86/mm/tlb.c > @@ -186,7 +186,11 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask, > > f->flush_mm = mm; > f->flush_va = va; > - if (cpumask_andnot(to_cpumask(f->flush_cpumask), cpumask, cpumask_of(smp_processor_id()))) { > + > + cpumask_and(to_cpumask(f->flush_cpumask), cpumask, cpu_online_mask); > + cpumask_clear_cpu(smp_processor_id(), to_cpumask(f->flush_cpumask)); > + > + if (!cpumask_empty(to_cpumask(f->flush_cpumask))) { FWIW, there's code in tip/x86/mm which reworks all that and flush_tlb_others_ipi along with the 32 TLB flush vectors are being removed in favor of a smp_call_function_many thing. And it should be hotplug-safe since it must be called with preemption disabled anyway. -- Regards/Gruss, Boris.