From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761286AbdADRc2 (ORCPT ); Wed, 4 Jan 2017 12:32:28 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50006 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752638AbdADRbj (ORCPT ); Wed, 4 Jan 2017 12:31:39 -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 , Stephen Hemminger Subject: [PATCH v2 3/4] hv_util: use do_adjtimex() to update system time Date: Wed, 4 Jan 2017 18:24:38 +0100 Message-Id: <20170104172439.19683-4-vkuznets@redhat.com> In-Reply-To: <20170104172439.19683-1-vkuznets@redhat.com> References: <20170104172439.19683-1-vkuznets@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Wed, 04 Jan 2017 17:24:49 +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(). Do do_settimeofday64() in case the difference is too big or ICTIMESYNCFLAG_SYNC flag was set in the request. Signed-off-by: Vitaly Kuznetsov --- Changes since v1: - do do_settimeofday64() when ICTIMESYNCFLAG_SYNC flag is present in the request (Alex Ng) - add pr_debug() for the case when do_adjtimex() fails (Alex Ng) --- drivers/hv/hv_util.c | 32 +++++++++++++++++++++++++++++--- 1 file changed, 29 insertions(+), 3 deletions(-) diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c index 94719eb..7e97231 100644 --- a/drivers/hv/hv_util.c +++ b/drivers/hv/hv_util.c @@ -182,9 +182,11 @@ 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}; + int ret; wrk = container_of(work, struct adj_time_work, work); @@ -205,7 +207,31 @@ 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; + + /* + * Do raw do_settimeofday64() in case delta is too big or we were + * ordered to sync our time by the host. + */ + if (abs(delta) > MAXPHASE || wrk->flags & ICTIMESYNCFLAG_SYNC) { + 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; + + ret = do_adjtimex(&txc); + if (ret) + pr_debug("Failed to adjust system time: %d\n", ret); } /* -- 2.9.3