From: David Vrabel <david.vrabel@citrix.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: <xen-devel@lists.xen.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
LKML <linux-kernel@vger.kernel.org>,
John Stultz <john.stultz@linaro.org>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 2/4] time: add a notifier chain for when the system time is stepped
Date: Fri, 21 Jun 2013 13:41:45 +0100 [thread overview]
Message-ID: <51C44A09.9010402@citrix.com> (raw)
In-Reply-To: <alpine.DEB.2.02.1306210953480.4013@ionos.tec.linutronix.de>
On 21/06/13 08:57, Thomas Gleixner wrote:
> On Thu, 20 Jun 2013, David Vrabel wrote:
>
>> From: David Vrabel <david.vrabel@citrix.com>
>>
>> The high resolution timer code gets notified of step changes to the
>> system time with clock_was_set() or clock_was_set_delayed() calls. If
>> other parts of the kernel require similar notification there is no
>> clear place to hook into.
>
> You fail to explain why any other part of the kernel requires a
> notification.
This is needed by patch 3 in this series.
"The Xen wallclock is a software only clock within the Xen hypervisor
that is used by: a) PV guests as the equivalent of a hardware RTC; and
b) the hypervisor as the clock source for the emulated RTC provided to
HVM guests.
Currently the Xen wallclock is only updated every 11 minutes if NTP is
synchronized to its clock source. If a guest is started before NTP is
synchronized it may see an incorrect wallclock time.
Use the clock_was_set notifier chain to receive a notification when
the system time is stepped and update the wallclock to match the
current system time."
> We went great length to confine timekeeping inside the core code and
> now you add random notifiers along with totally ugly tasklet
> constructs.
I'm not sure I understand your objection to the use of a tasklet. Using
the hrtimer softirq for something that is no longer hrtimer-specific did
not seem like the correct thing to do.
David
next prev parent reply other threads:[~2013-06-21 12:41 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-20 19:16 [PATCHv5 0/4] xen: maintain an accurate persistent clock in more cases David Vrabel
2013-06-20 19:16 ` [PATCH 1/4] hrtimers: provide a hrtimers_late_resume() call David Vrabel
2013-06-21 7:53 ` Thomas Gleixner
2013-06-21 12:32 ` David Vrabel
2013-06-21 14:32 ` Thomas Gleixner
2013-06-21 17:30 ` David Vrabel
2013-06-21 21:24 ` Thomas Gleixner
2013-06-20 19:16 ` [PATCH 2/4] time: add a notifier chain for when the system time is stepped David Vrabel
2013-06-21 7:57 ` Thomas Gleixner
2013-06-21 12:41 ` David Vrabel [this message]
2013-06-21 23:06 ` Thomas Gleixner
2013-06-24 10:51 ` David Vrabel
2013-06-24 16:30 ` Thomas Gleixner
2013-06-24 17:00 ` David Vrabel
2013-06-24 17:50 ` John Stultz
2013-06-24 19:55 ` Thomas Gleixner
2013-06-21 16:22 ` John Stultz
2013-06-20 19:16 ` [PATCH 3/4] x86/xen: sync the wallclock " David Vrabel
2013-06-20 19:16 ` [PATCH 4/4] x86/xen: sync the CMOS RTC as well as the Xen wallclock David Vrabel
2013-06-20 20:03 ` [PATCHv5 0/4] xen: maintain an accurate persistent clock in more cases John Stultz
2013-06-21 18:31 ` Konrad Rzeszutek Wilk
-- strict thread matches above, loose matches on Subject: below --
2013-06-19 15:25 [PATCHv4 " David Vrabel
2013-06-19 15:25 ` [PATCH 2/4] time: add a notifier chain for when the system time is stepped David Vrabel
2013-06-19 16:52 ` John Stultz
2013-06-19 17:13 ` Konrad Rzeszutek Wilk
2013-06-19 17:38 ` John Stultz
2013-06-20 10:50 ` David Vrabel
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