Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932154AbaKPUDH (ORCPT ); Sun, 16 Nov 2014 15:03:07 -0500 Received: from mail-vc0-f170.google.com ([209.85.220.170]:35197 "EHLO mail-vc0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751632AbaKPUDG (ORCPT ); Sun, 16 Nov 2014 15:03:06 -0500 MIME-Version: 1.0 In-Reply-To: <393289076.116745.1416126792518.open-xchange@webmail.nmp.skynet.be> References: <393289076.116745.1416126792518.open-xchange@webmail.nmp.skynet.be> Date: Sun, 16 Nov 2014 12:03:04 -0800 X-Google-Sender-Auth: z3oP-zKwfXyp-BjbGM0dHcBLLBY Message-ID: Subject: Re: frequent lockups in 3.18rc4: revert suggestion From: Linus Torvalds To: Fabian Frederick Cc: Dave Jones , linux-kernel , Thomas Gleixner , Ingo Molnar , "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 Sun, Nov 16, 2014 at 12:33 AM, Fabian Frederick wrote: > > Have you tried reverting the following patches (all from rc1) ? Hmm. Any particular reason you're looking at those? > c6f4459 v3.18-rc1 smp: Add new wake_up_all_idle_cpus() function > bb964a9 v3.18-rc1 kernel misc: Replace __get_cpu_var uses > 2ed903c v3.18-rc1 cpuidle: Use wake_up_all_idle_cpus() to wake up all idle cpus It does strike me that the reschedule IPI is somewhat special in that we don't try to serialize it at all, on the grounds that a lost IPI is ok (ie smp_send_reschedule() is very much a special case of IPI). Or am I mis-remembering? Does that series end up adding a lot more of those things, rather than using the normal smp_call_function(). The normal smp_function_mask() thing tries to make sure only one entry is ever active at a time (even a non-blocking one will use the whole "queue it on a llist, only send the IPI if the llist was empty", so this is not about the IPI's being synchronous). The rescheduling thing is rather special, isn't it. The softlockup thing *did* look like some IPI got lost. Could an IPI overflow on the RESCHEDULE_VECTOR end up affecting other vectors? It's been too long since I worked with the APIC (and by "too long", I obviously mean "thank God I haven't had to" ;^) but there used to be grouping of the vectors.. Maybe that is all barking up the wrong tree, but I'm wondering why Fabian picked that particular set of commits. Fabian? 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/