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=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 8A03DC10F0E for ; Tue, 9 Apr 2019 11:28:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 545872084C for ; Tue, 9 Apr 2019 11:28:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="fWaUpiWR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727229AbfDIL2q (ORCPT ); Tue, 9 Apr 2019 07:28:46 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:60714 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726129AbfDIL2p (ORCPT ); Tue, 9 Apr 2019 07:28:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=G6ULmSG0BNru+4dAKKU1SN0CstQxw7Ak6N5cxM5IRcE=; b=fWaUpiWRWuZHSwZ4uZovrsYFt rRxOVTHI4gv7Fnp4nTCSyAzZMvvxbjC9pkGPupAsZ5a3rekdXImiSv2brbh29JNZlAfzwg4+j1Qg2 m3RtwHoqcEYe5iaWZvFM2I4DIJXN2CjfzB1dZ1gPBmEcSE9oHdMeimmpJ+1tu2gAB2rFjuwzw1WBd Eelil2j8EnNJ9p4BXcaTAd/1OrEpdZG55SLShyRKz+wcp/cadnJxOE//kcuTfKTMdxK/qxK3GwOFl Vuypo3/GctcVnCY/kCj5/wtEogrIEueWOjsIU0+5QmxrdDVMmWn7sD9Qhqs6Odgxd6xim1WXdGrVn DBXCAvoiw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hDovL-00045Y-8c; Tue, 09 Apr 2019 11:28:19 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id B7409201F29BA; Tue, 9 Apr 2019 13:28:17 +0200 (CEST) Date: Tue, 9 Apr 2019 13:28:17 +0200 From: Peter Zijlstra To: Ricardo Neri Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Ashok Raj , Andi Kleen , "Ravi V. Shankar" , x86@kernel.org, linux-kernel@vger.kernel.org, Ricardo Neri , "H. Peter Anvin" , Tony Luck , Clemens Ladisch , Arnd Bergmann , Philippe Ombredanne , Kate Stewart , "Rafael J. Wysocki" , Mimi Zohar , Jan Kiszka , Nick Desaulniers , Masahiro Yamada , Nayna Jain Subject: Re: [RFC PATCH v2 12/14] x86/watchdog/hardlockup/hpet: Determine if HPET timer caused NMI Message-ID: <20190409112817.GT4038@hirez.programming.kicks-ass.net> References: <1551283518-18922-1-git-send-email-ricardo.neri-calderon@linux.intel.com> <1551283518-18922-13-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: <1551283518-18922-13-git-send-email-ricardo.neri-calderon@linux.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 27, 2019 at 08:05:16AM -0800, Ricardo Neri wrote: > @@ -62,7 +67,18 @@ static inline void set_comparator(struct hpet_hld_data *hdata, > static void kick_timer(struct hpet_hld_data *hdata, bool force) > { > bool kick_needed = force || !(hdata->flags & HPET_DEV_PERI_CAP); > - unsigned long new_compare, count; > + unsigned long tsc_curr, tsc_delta, new_compare, count; > + > + /* Start obtaining the current TSC and HPET counts. */ > + tsc_curr = rdtsc(); > + > + if (kick_needed) > + count = get_count(); > + > + tsc_delta = (unsigned long)watchdog_thresh * (unsigned long)tsc_khz > + * 1000L; > + hdata->tsc_next = tsc_curr + tsc_delta; > + hdata->tsc_next_error = tsc_delta >> 6; What do we need a per hld_data tsc_next_error for? It is basically a global 'constant'. > /* > * Update the comparator in increments of watch_thresh seconds relative > @@ -74,8 +90,6 @@ static void kick_timer(struct hpet_hld_data *hdata, bool force) > */ > > if (kick_needed) { > - count = get_count(); > - > new_compare = count + watchdog_thresh * hdata->ticks_per_second; > > set_comparator(hdata, new_compare); > @@ -147,6 +161,14 @@ static void set_periodic(struct hpet_hld_data *hdata) > */ > static bool is_hpet_wdt_interrupt(struct hpet_hld_data *hdata) > { > + if (smp_processor_id() == hdata->handling_cpu) { > + unsigned long tsc_curr; TSC is u64 > + > + tsc_curr = rdtsc(); > + if (abs(tsc_curr - hdata->tsc_next) < hdata->tsc_next_error) > + return true; You can write that as: (tsc_curr - hdata->tsc_next) + tsc_error < 2*tsc_error which doesn't contain any branches what so ever. > + } > + > return false; > }