From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752975AbdCVUT3 (ORCPT ); Wed, 22 Mar 2017 16:19:29 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:44566 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752831AbdCVUTH (ORCPT ); Wed, 22 Mar 2017 16:19:07 -0400 From: Pavel Tatashin To: x86@kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, tglx@linutronix.de, hpa@zytor.com Subject: [v1 1/9] sched/clock: broken stable to unstable transfer Date: Wed, 22 Mar 2017 16:24:17 -0400 Message-Id: <1490214265-899964-2-git-send-email-pasha.tatashin@oracle.com> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1490214265-899964-1-git-send-email-pasha.tatashin@oracle.com> References: <1490214265-899964-1-git-send-email-pasha.tatashin@oracle.com> X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When it is determined that clock is actually unstable, and we switch from stable to unstable the following function is eventually called: __clear_sched_clock_stable() In this function we set gtod_offset so the following holds true: sched_clock() + raw_offset == ktime_get_ns() + gtod_offset But instead of getting the latest timestamps, we use the last values from scd, so instead of sched_clock() we use scd->tick_raw, and instead of ktime_get_ns() we use scd->tick_gtod. However, later, when we use gtod_offset sched_clock_local() we do not add it to scd->tick_gtod to calculate the correct clock value when we determine the boundaries for min/max clocks. Signed-off-by: Pavel Tatashin --- kernel/sched/clock.c | 9 +++++---- 1 files changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index a08795e..2bc1090 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -214,7 +214,7 @@ static inline u64 wrap_max(u64 x, u64 y) */ static u64 sched_clock_local(struct sched_clock_data *scd) { - u64 now, clock, old_clock, min_clock, max_clock; + u64 now, clock, old_clock, min_clock, max_clock, gtod; s64 delta; again: @@ -231,9 +231,10 @@ static u64 sched_clock_local(struct sched_clock_data *scd) * scd->tick_gtod + TICK_NSEC); */ - clock = scd->tick_gtod + gtod_offset + delta; - min_clock = wrap_max(scd->tick_gtod, old_clock); - max_clock = wrap_max(old_clock, scd->tick_gtod + TICK_NSEC); + gtod = scd->tick_gtod + gtod_offset; + clock = gtod + delta; + min_clock = wrap_max(gtod, old_clock); + max_clock = wrap_max(old_clock, gtod + TICK_NSEC); clock = wrap_max(clock, min_clock); clock = wrap_min(clock, max_clock); -- 1.7.1