From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756664AbdABTmf (ORCPT ); Mon, 2 Jan 2017 14:42:35 -0500 Received: from mx1.redhat.com ([209.132.183.28]:45480 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933998AbdABTlX (ORCPT ); Mon, 2 Jan 2017 14:41:23 -0500 From: Vitaly Kuznetsov To: devel@linuxdriverproject.org Cc: linux-kernel@vger.kernel.org, "K. Y. Srinivasan" , Haiyang Zhang , John Stultz , Thomas Gleixner , Alex Ng Subject: [PATCH 3/4] hv_util: use do_adjtimex() to update system time Date: Mon, 2 Jan 2017 20:41:13 +0100 Message-Id: <20170102194114.657-4-vkuznets@redhat.com> In-Reply-To: <20170102194114.657-1-vkuznets@redhat.com> References: <20170102194114.657-1-vkuznets@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 02 Jan 2017 19:41:23 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With TimeSync version 4 protocol support we started updating system time continuously through the whole lifetime of Hyper-V guests. Every 5 seconds there is a time sample from the host which triggers do_settimeofday[64](). While the time from the host is very accurate such adjustments may cause issues: - Time is jumping forward and backward, some applications may misbehave. - In case an NTP client is run in parallel things may go south, e.g. when an NTP client tries to adjust tick/frequency with ADJ_TICK/ADJ_FREQUENCY the Hyper-V module will not see this changes and time will oscillate and never converge. - Systemd starts annoying you by printing "Time has been changed" every 5 seconds to the system log. Instead of calling do_settimeofday64() we can pretend being an NTP client and use do_adjtimex(). Signed-off-by: Vitaly Kuznetsov --- drivers/hv/hv_util.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-) diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c index 94719eb..4c0fbb0 100644 --- a/drivers/hv/hv_util.c +++ b/drivers/hv/hv_util.c @@ -182,9 +182,10 @@ struct adj_time_work { static void hv_set_host_time(struct work_struct *work) { struct adj_time_work *wrk; - s64 host_tns; + s64 host_tns, our_tns, delta; u64 newtime; - struct timespec64 host_ts; + struct timespec64 host_ts, our_ts; + struct timex txc = {0}; wrk = container_of(work, struct adj_time_work, work); @@ -205,7 +206,25 @@ static void hv_set_host_time(struct work_struct *work) host_tns = (newtime - WLTIMEDELTA) * 100; host_ts = ns_to_timespec64(host_tns); - do_settimeofday64(&host_ts); + getnstimeofday64(&our_ts); + our_tns = timespec64_to_ns(&our_ts); + + /* Difference between our time and host time */ + delta = host_tns - our_tns; + + /* Try adjusting time by using phase adjustment if possible */ + if (abs(delta) > MAXPHASE) { + do_settimeofday64(&host_ts); + return; + } + + txc.modes = ADJ_TICK | ADJ_FREQUENCY | ADJ_OFFSET | ADJ_NANO | + ADJ_STATUS; + txc.tick = TICK_USEC; + txc.freq = 0; + txc.status = STA_PLL; + txc.offset = delta; + do_adjtimex(&txc); } /* -- 2.9.3