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Date: Thu, 5 Aug 2010 15:39:28 +0300
Message-ID: <AANLkTimTDbyn+RA=FHii=vGFypO_O1EjpmdYU4h2_vd8@mail.gmail.com>
Subject: Re: [PATCH] [RFC] notify userspace about time changes
From: Alexander Shishkin <virtuoso@slind.org>
To: john stultz <johnstul@us.ibm.com>
Cc: Chris Friesen <chris.friesen@genband.com>, gregkh@suse.de,
        lkml@vger.kernel.org, "Kirill A. Shutemov" <kirill@shutemov.name>,
        Thomas Gleixner <tglx@linutronix.de>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jon Hunter <jon-hunter@ti.com>, Ingo Molnar <mingo@elte.hu>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        David Howells <dhowells@redhat.com>, Avi Kivity <avi@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, John Kacur <jkacur@redhat.com>,
        linux-kernel@vger.kernel.org
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On 5 August 2010 03:52, john stultz <johnstul@us.ibm.com> wrote:
> On Wed, 2010-08-04 at 12:48 -0600, Chris Friesen wrote:
>> On 08/04/2010 09:58 AM, john stultz wrote:
>>
>> > Is there a actual use case that you need this for?  I don't really have
>> > an issue with the code I just really want to make sure the feature would
>> > be useful enough to justify the API and code maintenance going forward.
>>
>> We actually added a time-change-notification mechanism internally a long
>> time ago but never saw demand for it and so never bothered trying to
>> push it upstream.  Ours is signal-based.
>>
>> Among other things we use it to pass on time-change notifications to an
>> emulator running a proprietary OS that really cares about having an
>> accurate time-of-day but can't afford a syscall to retrieve it every time.
>
> So the eventfd based method (and the filtering) proposed would work for
> you?

I think that Kirill has a point and the filtering is really there for
no gain. The user
can indeed count his own time changes and compare that against the eventfd
counter.

Regards,
--
Alex
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