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 AF63CC7618D for ; Thu, 6 Apr 2023 04:17:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235148AbjDFERe (ORCPT ); Thu, 6 Apr 2023 00:17:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37732 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233641AbjDFERc (ORCPT ); Thu, 6 Apr 2023 00:17:32 -0400 X-Greylist: delayed 472 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Wed, 05 Apr 2023 21:17:31 PDT Received: from smtp-out0.aaront.org (smtp-out0.aaront.org [52.10.12.108]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2F74B8690 for ; Wed, 5 Apr 2023 21:17:30 -0700 (PDT) Received: by smtp-out0.aaront.org (Postfix) with ESMTP id 4PsSgj51ydzJQ; Thu, 6 Apr 2023 04:09:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=aaront.org; h= from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; s=elwxqanhxhag6erl; bh=NASh0ELdjVlYA TWtGAhESwP0/qGYU3DPBNFRmdeYc2w=; b=wh6d82KTw6M1wbyCg3biZskqEuiDf 65Iz5kDiNrEn3tsXb8iZUZmdDYz9uU2eeM/WvRgACEVh+WBWN6Uy9KCkValuSWhm XbFi+q1YmKcrY2D901g/k2sqdX72xsHhJbQlSU7Mp3JOdbbDZifVsKczcU5c/0kh 1DOgqrJ2X7vIcyZsMrBvUCTlvIftFcRRLSFyHxSO/cO5voIcUi58H57pIYUtXWvX 7hodtwKGAoTBvZoXUeyj6X+XaWBVwqlpwvvewJIslcTcVmEtbW5Bkj3O9AF//M2v qNVLJSMBm1C+AWQz+fKuIMszKxKqAZKrB1omxDsGi+0qQJ/ccK9qeEcnw== From: Aaron Thompson To: Ingo Molnar , Peter Zijlstra Cc: Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , linux-kernel@vger.kernel.org, Aaron Thompson Subject: [PATCH] sched/clock: Fix local_clock() before sched_clock_init() Date: Thu, 6 Apr 2023 04:08:47 +0000 Message-Id: <20230406040847.569970-1-dev@aaront.org> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Have local_clock() return sched_clock() if sched_clock_init() has not yet run. sched_clock_cpu() has this check but it was not included in the new noinstr implementation of local_clock(). The effect can be seen on x86 with CONFIG_PRINTK_TIME enabled, for instance. scd->clock quickly reaches the value of TICK_NSEC and that value is returned until sched_clock_init() runs. dmesg without this patch: [ 0.000000] kvm-clock: ... [ 0.000002] kvm-clock: ... [ 0.000672] clocksource: ... [ 0.001000] tsc: ... [ 0.001000] e820: ... [ 0.001000] e820: ... ... [ 0.001000] ..TIMER: ... [ 0.001000] clocksource: ... [ 0.378956] Calibrating delay loop ... [ 0.379955] pid_max: ... dmesg with this patch: [ 0.000000] kvm-clock: ... [ 0.000001] kvm-clock: ... [ 0.000675] clocksource: ... [ 0.002685] tsc: ... [ 0.003331] e820: ... [ 0.004190] e820: ... ... [ 0.421939] ..TIMER: ... [ 0.422842] clocksource: ... [ 0.424582] Calibrating delay loop ... [ 0.425580] pid_max: ... Fixes: 776f22913b8e ("sched/clock: Make local_clock() noinstr") Signed-off-by: Aaron Thompson --- kernel/sched/clock.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index 5732fa75ebab..b5cc2b53464d 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -300,6 +300,9 @@ noinstr u64 local_clock(void) if (static_branch_likely(&__sched_clock_stable)) return sched_clock() + __sched_clock_offset; + if (!static_branch_likely(&sched_clock_running)) + return sched_clock(); + preempt_disable_notrace(); clock = sched_clock_local(this_scd()); preempt_enable_notrace(); -- 2.39.2