Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753254AbbDBRfp (ORCPT ); Thu, 2 Apr 2015 13:35:45 -0400 Received: from mail-ig0-f175.google.com ([209.85.213.175]:36395 "EHLO mail-ig0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751360AbbDBRfo (ORCPT ); Thu, 2 Apr 2015 13:35:44 -0400 MIME-Version: 1.0 In-Reply-To: <20150402095533.GA4968@gmail.com> References: <20150331031536.GA9303@canonical.com> <20150331222327.GA12512@canonical.com> <20150401143236.GB12730@canonical.com> <20150402095533.GA4968@gmail.com> Date: Thu, 2 Apr 2015 10:35:43 -0700 X-Google-Sender-Auth: hldPuby0sExS85YaewJ0nd7Ckic Message-ID: Subject: Re: smp_call_function_single lockups From: Linus Torvalds To: Ingo Molnar Cc: Chris J Arges , Rafael David Tinoco , Peter Anvin , Jiang Liu , Peter Zijlstra , LKML , Jens Axboe , Frederic Weisbecker , Gema Gomez , "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 Content-Length: 908 Lines: 21 On Thu, Apr 2, 2015 at 2:55 AM, Ingo Molnar wrote: > > So another possibility would be that it's the third change causing > this change in behavior: Oh, yes, that looks much more likely. I overlooked that small change entirely. > ... since with this we won't send IPIs in a semi-nested fashion with > an unacked APIC, which is a good idea to do in general. It's also a > weird enough hardware pattern that virtualization's APIC emulation > might get it slightly wrong or slightly different. Yup, that's more likely than the subtle timing/reordering differences of just the added debug printouts. I agree. Linus -- 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/