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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 167EBC433B4 for ; Sat, 17 Apr 2021 23:43:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D889F6121D for ; Sat, 17 Apr 2021 23:43:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235826AbhDQXnZ (ORCPT ); Sat, 17 Apr 2021 19:43:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:53902 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229865AbhDQXnY (ORCPT ); Sat, 17 Apr 2021 19:43:24 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 486DB6121D; Sat, 17 Apr 2021 23:42:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1618702977; bh=gbxJJgwzLRLnhX1i6KaId8XkJ7sBCOQyVwkRfcOf/pM=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=OkWpgOHcK5Uvgl/EBuOJA0YHPNzOqIn+0fTpxEpYPQyLAgf/yIjU8Doq77Fz3oJIy VdPhPmuLT0WaPKBqIQUtP3ouvIsL2HPEL2HyEGLm7VSkqnPHVHmMASmFPSNEynp0vj FBhNfc+9iljiN2XLj2Orw8VGn4NsHs1gKIMha35DTVmMRFelFSzc6Br/KVfhW4CksX vQRDbj4z6DKhL0UHEffLXz0TGGYKHaOzLp80MvvFhe1ZsaWO823XfXk3jqyoyg34Z5 3R+5NZbekBCCRxhX6TQurUHbkS3VPDCHzl/FzSUU1BjQ0mt2JzrcwWxJG8Hd3KrX2A qGmc3ZiBbBLZA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 154225C051E; Sat, 17 Apr 2021 16:42:57 -0700 (PDT) Date: Sat, 17 Apr 2021 16:42:57 -0700 From: "Paul E. McKenney" To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org, john.stultz@linaro.org, sboyd@kernel.org, corbet@lwn.net, Mark.Rutland@arm.com, maz@kernel.org, kernel-team@fb.com, neeraju@codeaurora.org, ak@linux.intel.com, Chris Mason Subject: Re: [PATCH v8 clocksource 3/5] clocksource: Check per-CPU clock synchronization when marked unstable Message-ID: <20210417234257.GC5006@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20210414043435.GA2812539@paulmck-ThinkPad-P17-Gen-1> <20210414043602.2812981-3-paulmck@kernel.org> <87v98lrt7d.ffs@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87v98lrt7d.ffs@nanos.tec.linutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Apr 17, 2021 at 02:28:22PM +0200, Thomas Gleixner wrote: > On Tue, Apr 13 2021 at 21:36, Paul E. McKenney wrote: > > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c > > index 1fc0962c89c0..97eeaf164296 100644 > > --- a/arch/x86/kernel/kvmclock.c > > +++ b/arch/x86/kernel/kvmclock.c > > @@ -169,7 +169,7 @@ struct clocksource kvm_clock = { > > .read = kvm_clock_get_cycles, > > .rating = 400, > > .mask = CLOCKSOURCE_MASK(64), > > - .flags = CLOCK_SOURCE_IS_CONTINUOUS, > > + .flags = CLOCK_SOURCE_IS_CONTINUOUS | CLOCK_SOURCE_VERIFY_PERCPU, > > kvm_clock is not marked with CLOCK_SOURCE_MUST_VERIFY, so what's the > point of adding this here? It's not subject to be monitored by the > watchdog muck. Good point, removed. > > diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c > > index f70dffc2771f..56289170753c 100644 > > --- a/arch/x86/kernel/tsc.c > > +++ b/arch/x86/kernel/tsc.c > > @@ -1151,7 +1151,8 @@ static struct clocksource clocksource_tsc = { > > .mask = CLOCKSOURCE_MASK(64), > > .flags = CLOCK_SOURCE_IS_CONTINUOUS | > > CLOCK_SOURCE_VALID_FOR_HRES | > > - CLOCK_SOURCE_MUST_VERIFY, > > + CLOCK_SOURCE_MUST_VERIFY | > > + CLOCK_SOURCE_VERIFY_PERCPU, > > While this one is part of the horror show. It probably would be good to decorate other arch's per-CPU clocks with CLOCK_SOURCE_VERIFY_PERCPU, but no takers thus far. Thanx, Paul > > +static u64 csnow_mid; > > +static cpumask_t cpus_ahead; > > +static cpumask_t cpus_behind; > > + > > +static void clocksource_verify_one_cpu(void *csin) > > +{ > > + struct clocksource *cs = (struct clocksource *)csin; > > + > > + csnow_mid = cs->read(cs); > > +} > > + > > +static void clocksource_verify_percpu(struct clocksource *cs) > > +{ > > + int64_t cs_nsec, cs_nsec_max, cs_nsec_min; > > + u64 csnow_begin, csnow_end; > > + bool firsttime = 1; > > + int testcpu; > > + s64 delta; > > + int cpu; > > int testcpu, cpu; :) >