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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 B8924C433DF for ; Wed, 20 May 2020 19:51:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8B76C207E8 for ; Wed, 20 May 2020 19:51:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726985AbgETTvd (ORCPT ); Wed, 20 May 2020 15:51:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50360 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726818AbgETTvd (ORCPT ); Wed, 20 May 2020 15:51:33 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4DFAC061A0E for ; Wed, 20 May 2020 12:51:32 -0700 (PDT) Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jbUkC-0001ev-0Q; Wed, 20 May 2020 21:51:12 +0200 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id 659B8100C99; Wed, 20 May 2020 21:51:11 +0200 (CEST) From: Thomas Gleixner To: Steven Rostedt Cc: LKML , x86@kernel.org, "Paul E. McKenney" , Andy Lutomirski , Alexandre Chartre , Frederic Weisbecker , Paolo Bonzini , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Mathieu Desnoyers , Josh Poimboeuf , Will Deacon , Tom Lendacky , Wei Liu , Michael Kelley , Jason Chen CJ , Zhao Yakui , "Peter Zijlstra \(Intel\)" Subject: Re: [patch V6 01/37] tracing/hwlat: Use ktime_get_mono_fast_ns() In-Reply-To: <20200519181802.5c88c557@gandalf.local.home> References: <20200515234547.710474468@linutronix.de> <20200515235124.466962628@linutronix.de> <20200519172627.7e65669e@gandalf.local.home> <871rnf7g61.fsf@nanos.tec.linutronix.de> <20200519181802.5c88c557@gandalf.local.home> Date: Wed, 20 May 2020 21:51:11 +0200 Message-ID: <87lflmv100.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Steven Rostedt writes: > On Tue, 19 May 2020 23:45:10 +0200 > Thomas Gleixner wrote: > >> >> @@ -165,20 +155,22 @@ void trace_hwlat_callback(bool enter) >> >> * Used to repeatedly capture the CPU TSC (or similar), looking for potential >> >> * hardware-induced latency. Called with interrupts disabled and with >> >> * hwlat_data.lock held. >> >> + * >> >> + * Use ktime_get_mono_fast() here as well because it does not wait on the >> >> + * timekeeping seqcount like ktime_get_mono(). >> > >> > When doing a "git grep ktime_get_mono" I only find >> > ktime_get_mono_fast_ns() (and this comment), so I don't know what to compare >> > that to. Did you mean another function? >> >> Yeah. I fatfingered the comment. The code uses ktime_get_mono_fast_ns(). > > Well, I assumed that's what you meant with "ktime_get_mono_fast()" but I > don't know what function you are comparing it to that waits on the seqcount > like "ktime_get_mono()" as there is no such function. Gah. ktime_get_mono_fast_ns() and ktime_get() of course.