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From: John Baldwin <jhb@freebsd.org>
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Date: Mon, 29 Mar 2010 10:44:28 -0400
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Cc: Dag-Erling =?utf-8?q?Sm=C3=B8rgrav?= <des@des.no>,
	Andriy Gapon <avg@icyb.net.ua>
Subject: Re: periodically save current time to time-of-day hardware
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On Sunday 28 March 2010 7:45:25 am Dag-Erling Sm=C3=B8rgrav wrote:
> Peter Jeremy <peterjeremy@acm.org> writes:
> > A new kthread which sleeps on channel "update_rtc".  When woken, it
> > checks to see if it's within (say) 50msec of a second boundary and so,
> > it does a trylock on the (new) RTC mutex.  If it grabs the mutex then
> > it performs the update.  If it was too far from the second boundary or
> > it fails to grab the mutex then it sleeps until the next second
> > boundary and tries again.
> >
> > The existing resettodr() would then turn into a wakeup(update_rtc).
>=20
> Sounds good to me, but if only that thread has access to the RTC, why
> bother with a mutex?

I would dispense with the kthread and just use a callout (or have a callout=
=20
schedule a task for taskqueue_thread).

=2D-=20
John Baldwin