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Re: [rtc-linux] Re: [RFC][PATCH 1/4] RTC: Class device support for persi

Subject: Re: [rtc-linux] Re: [RFC][PATCH 1/4] RTC: Class device support for persistent clock
From: Alessandro Zummo <>
Date: Wed, 7 May 2008 13:49:30 +0200
Cc:, Ralf Baechle <>, Thomas Gleixner <>, Andrew Morton <>,,
In-reply-to: <>
Organization: Tower Technologies
Original-recipient: rfc822;
References: <> <>
On Wed, 07 May 2008 09:24:15 +0100
David Woodhouse <> wrote:

> Ooh, shiny -- you saved me the trouble of doing this (and hopefully also
> the trouble of looking through it to check whether all the callers of
> read_persistent_clock() can sleep, etc.?)

 I knew you would have liked that patch :)
> One thing I was going to do in rtc_update_persistent_clock() was make it
> use mutex_trylock() for grabbing rtc->lock. We go to great lengths to
> make sure we're updating the clock at the correct time -- we don't want
> to be doing things which delay the update. So we should probably just
> use mutex_trylock() and abort the update (this time) if it fails.

> I was also thinking of holding the RTC_HCTOSYS device open all the time,
> too. If it's a problem that you then couldn't unload the module, perhaps
> a sysfs interface to set/change/clear which device is used for this?

 mm.. let's keep it easy. the chances the rtc is in use
 are usually real low.


 Best regards,

 Alessandro Zummo,
  Tower Technologies - Torino, Italy

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