From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752298AbbBSQ0Z (ORCPT ); Thu, 19 Feb 2015 11:26:25 -0500 Received: from mail-ie0-f176.google.com ([209.85.223.176]:41384 "EHLO mail-ie0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751681AbbBSQ0Y (ORCPT ); Thu, 19 Feb 2015 11:26:24 -0500 MIME-Version: 1.0 In-Reply-To: References: <20150218222544.GA17717@twins.programming.kicks-ass.net> Date: Thu, 19 Feb 2015 08:26:23 -0800 X-Google-Sender-Auth: lk0JcXJlGomLfIYWxnMxMa-mWh0 Message-ID: Subject: Re: smp_call_function_single lockups From: Linus Torvalds To: Rafael David Tinoco Cc: Peter Zijlstra , LKML , Jens Axboe , Frederic Weisbecker , Gema Gomez , chris.j.arges@canonical.com, "the arch/x86 maintainers" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 19, 2015 at 7:42 AM, Rafael David Tinoco wrote: > > Same environment as before: Nested KVM (2 vcpus) on top of Proliant > DL380G8 with acpi_idle and no x2apic optout. Btw, which apic model does that end up using? Does "no x2apic optout" mean you're using the x2apic? What does "dmesg | grep apic" report? Something like Switched APIC routing to cluster x2apic. or what? Side note to the apic guys: I think the "single CPU" case ends up being one of the most important ones, but the stupid APIC model doesn't allow that, so sending an IPI to a single CPU ends up being "send a mask with a single bit set", and then we have that horrible "for_each_cpu(cpu, mask)" crap. Would it make sense to perhaps add a "send_IPI_single()" function call, and then for the APIC models that always are based on masks, use a wrapper that just does that "cpumask_of(cpu)" thing.. Hmm? Linus