From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752450AbdC0KbB (ORCPT ); Mon, 27 Mar 2017 06:31:01 -0400 Received: from terminus.zytor.com ([65.50.211.136]:55517 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752037AbdC0Kax (ORCPT ); Mon, 27 Mar 2017 06:30:53 -0400 Date: Mon, 27 Mar 2017 03:27:22 -0700 From: tip-bot for Pavel Tatashin Message-ID: Cc: tglx@linutronix.de, torvalds@linux-foundation.org, peterz@infradead.org, mingo@kernel.org, linux-kernel@vger.kernel.org, hpa@zytor.com, pasha.tatashin@oracle.com Reply-To: pasha.tatashin@oracle.com, linux-kernel@vger.kernel.org, hpa@zytor.com, torvalds@linux-foundation.org, peterz@infradead.org, mingo@kernel.org, tglx@linutronix.de In-Reply-To: <1490214265-899964-2-git-send-email-pasha.tatashin@oracle.com> References: <1490214265-899964-2-git-send-email-pasha.tatashin@oracle.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] sched/clock: Fix broken stable to unstable transfer Git-Commit-ID: 7b09cc5a9debc86c903c2eff8f8a1fdef773c649 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 7b09cc5a9debc86c903c2eff8f8a1fdef773c649 Gitweb: http://git.kernel.org/tip/7b09cc5a9debc86c903c2eff8f8a1fdef773c649 Author: Pavel Tatashin AuthorDate: Wed, 22 Mar 2017 16:24:17 -0400 Committer: Ingo Molnar CommitDate: Mon, 27 Mar 2017 10:23:48 +0200 sched/clock: Fix broken stable to unstable transfer When it is determined that the clock is actually unstable, and we switch from stable to unstable, the __clear_sched_clock_stable() function is eventually called. 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. This can result in tick granularity sched_clock() values, so fix it. Signed-off-by: Pavel Tatashin Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: hpa@zytor.com Fixes: 5680d8094ffa ("sched/clock: Provide better clock continuity") Link: http://lkml.kernel.org/r/1490214265-899964-2-git-send-email-pasha.tatashin@oracle.com Signed-off-by: Ingo Molnar --- kernel/sched/clock.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index 24a3e01..00a45c4 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -221,7 +221,7 @@ 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: @@ -238,9 +238,10 @@ again: * 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);