From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 849B6C433F5 for ; Fri, 13 May 2022 23:13:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229620AbiEMXNX (ORCPT ); Fri, 13 May 2022 19:13:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44334 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234885AbiEMXNU (ORCPT ); Fri, 13 May 2022 19:13:20 -0400 Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F072E307DB7 for ; Fri, 13 May 2022 16:13:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1652483586; x=1684019586; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=RwN3h2frQEmuTLpALiwJVKiux9iit8+Y3qd7tVOSlJg=; b=fxmXik6QJGG2xgOwrO8vrWaONEC4D1f4qqzWNqk3NVF7ODugy+oGqFeW cgRGxbXUsqSGRWNXerAlwzB0c9SF9L+Ph07ZBCpy1e5XIOWYMA3qnrse5 6qNC0bOsapAunq70VxYaUDbyn6N2+BibB0Hwr1TssmEyxwCVhhxb0gLQO pK5Bz9Dt3emKEUfHElK7cEPy0w0vdL7mFNgDWWc0iV3BpgGq27KOWXkDT SiHT0qMqZVuaUX/YweI2qXkpAfU0j87v3Lw007ak+f5r8mcrl0NP22VyO /UqMJizdvnyYDkMYKJL1mzjmiC65RSc6T363Q44OAq/BJY9zFqjLff9A8 Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10346"; a="252479209" X-IronPort-AV: E=Sophos;i="5.91,223,1647327600"; d="scan'208";a="252479209" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 May 2022 16:13:05 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.91,223,1647327600"; d="scan'208";a="573202350" Received: from ranerica-svr.sc.intel.com ([172.25.110.23]) by fmsmga007.fm.intel.com with ESMTP; 13 May 2022 16:13:04 -0700 Date: Fri, 13 May 2022 16:16:40 -0700 From: Ricardo Neri To: Nicholas Piggin Cc: Thomas Gleixner , x86@kernel.org, Andi Kleen , Andrew Morton , Lu Baolu , David Woodhouse , Stephane Eranian , iommu@lists.linux-foundation.org, Joerg Roedel , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, "Ravi V. Shankar" , Ricardo Neri , Suravee Suthikulpanit , Tony Luck Subject: Re: [PATCH v6 20/29] init/main: Delay initialization of the lockup detector after smp_init() Message-ID: <20220513231640.GA9074@ranerica-svr.sc.intel.com> References: <20220506000008.30892-1-ricardo.neri-calderon@linux.intel.com> <20220506000008.30892-21-ricardo.neri-calderon@linux.intel.com> <1652178524.7j2o02lrl8.astroid@bobo.none> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1652178524.7j2o02lrl8.astroid@bobo.none> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 10, 2022 at 08:38:22PM +1000, Nicholas Piggin wrote: > Excerpts from Ricardo Neri's message of May 6, 2022 9:59 am: > > Certain implementations of the hardlockup detector require support for > > Inter-Processor Interrupt shorthands. On x86, support for these can only > > be determined after all the possible CPUs have booted once (in > > smp_init()). Other architectures may not need such check. > > > > lockup_detector_init() only performs the initializations of data > > structures of the lockup detector. Hence, there are no dependencies on > > smp_init(). > Thank you for your feedback Nicholas! > I think this is the only real thing which affects other watchdog types? Also patches 18 and 19 that decouple the NMI watchdog functionality from perf. > > Not sure if it's a big problem, the secondary CPUs coming up won't > have their watchdog active until quite late, and the primary could > implement its own timeout in __cpu_up for secondary coming up, and > IPI it to get traces if necessary which is probably more robust. Indeed that could work. Another alternative I have been pondering is to boot the system with the perf-based NMI watchdog enabled. Once all CPUs are up and running, switch to the HPET-based NMI watchdog and free the PMU counters. > > Acked-by: Nicholas Piggin Thank you! BR, Ricardo