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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26748C31E5E for ; Tue, 18 Jun 2019 22:47:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 07662214AF for ; Tue, 18 Jun 2019 22:47:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730950AbfFRWrR (ORCPT ); Tue, 18 Jun 2019 18:47:17 -0400 Received: from mga05.intel.com ([192.55.52.43]:51550 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730341AbfFRWrR (ORCPT ); Tue, 18 Jun 2019 18:47:17 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 18 Jun 2019 15:47:16 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,390,1557212400"; d="scan'208";a="160196036" Received: from ranerica-svr.sc.intel.com ([172.25.110.23]) by fmsmga008.fm.intel.com with ESMTP; 18 Jun 2019 15:47:16 -0700 Date: Tue, 18 Jun 2019 15:46:54 -0700 From: Ricardo Neri To: Thomas Gleixner Cc: Ingo Molnar , Borislav Petkov , Ashok Raj , Joerg Roedel , Andi Kleen , Peter Zijlstra , Suravee Suthikulpanit , Stephane Eranian , "Ravi V. Shankar" , Randy Dunlap , x86@kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Ricardo Neri , Tony Luck , Jacob Pan , "Rafael J. Wysocki" , Don Zickus , Nicholas Piggin , Michael Ellerman , Frederic Weisbecker , Alexei Starovoitov , Babu Moger , Mathieu Desnoyers , Masami Hiramatsu , Andrew Morton , Philippe Ombredanne , Colin Ian King , Byungchul Park , "Paul E. McKenney" , "Luis R. Rodriguez" , Waiman Long , Josh Poimboeuf , Davidlohr Bueso , Marc Zyngier , Kai-Heng Feng , Konrad Rzeszutek Wilk , David Rientjes Subject: Re: [RFC PATCH v4 12/21] watchdog/hardlockup/hpet: Adjust timer expiration on the number of monitored CPUs Message-ID: <20190618224654.GB30488@ranerica-svr.sc.intel.com> References: <1558660583-28561-1-git-send-email-ricardo.neri-calderon@linux.intel.com> <1558660583-28561-13-git-send-email-ricardo.neri-calderon@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 11, 2019 at 10:11:04PM +0200, Thomas Gleixner wrote: > On Thu, 23 May 2019, Ricardo Neri wrote: > > @@ -52,10 +59,10 @@ static void kick_timer(struct hpet_hld_data *hdata, bool force) > > return; > > > > if (hdata->has_periodic) > > - period = watchdog_thresh * hdata->ticks_per_second; > > + period = watchdog_thresh * hdata->ticks_per_cpu; > > > > count = hpet_readl(HPET_COUNTER); > > - new_compare = count + watchdog_thresh * hdata->ticks_per_second; > > + new_compare = count + watchdog_thresh * hdata->ticks_per_cpu; > > hpet_set_comparator(hdata->num, (u32)new_compare, (u32)period); > > So with this you might get close to the point where you trip over the SMI > induced madness where CPUs vanish for several milliseconds in some value > add code. You really want to do a read back of the hpet to detect that. See > the comment in the hpet code. RHEL 7/8 allow up to 768 logical CPUs.... Do you mean adding a readback to check if the new compare value is greater than the current count? Similar to the check at the end of hpet_next_event(): return res < HPET_MIN_CYCLES ? -ETIME : 0; In such a case, should it try to set the comparator again? I think it should, as otherwise the hardlockup detector would stop working. Thanks and BR, Ricardo > > Thanks, > > tglx