linux-kernel - Re: [PATCHv6 0/7] system time changes notification

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Date:	Thu, 11 Nov 2010 18:35:51 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Thomas Gleixner <tglx@...utronix.de>
cc:	Kyle Moffett <kyle@...fetthome.net>,
	Alexander Shishkin <virtuoso@...nd.org>,
	Valdis.Kletnieks@...edu, LKML <linux-kernel@...r.kernel.org>,
	John Stultz <johnstul@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Kay Sievers <kay.sievers@...y.org>, Greg KH <gregkh@...e.de>,
	Chris Friesen <chris.friesen@...band.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill@...temov.name>
Subject: Re: [PATCHv6 0/7] system time changes notification

On Thu, 11 Nov 2010, Thomas Gleixner wrote:

> > [...]
> > 
> > This would also enable the folks who want to support things like PHY
> > hardware clocks (for very-low-latency ethernet timestamping).  It
> > would resolve the enumeration problem; instead of 0, 1, 2, ... as
> > constants, they would show up in sysfs and be open()able.  Ideally you
> > would be able to set up ntpd to slew the "realtime" clock by following
> > a particular hardware clock, or vice versa.
> 
> There are other plans for the various interesting clocks floating
> around which look pretty good.
> 
> But what you folks really want for this stuff is an extension to
> timerfd as you want to be able to poll, right?
> 
> So what about the following:
> 
> Add a new flag TDF_NOTIFY_CLOCK_WAS_SET to the timerfd flags. Now this
> flag adds the timer to a separate list, which gets woken up when the
> clock is set.

What chu talkin bout Willis? :)
This borders the interface multiplexing, if I got your idea correctly.
Timerfd is about expiring private timers, not about getting out 
notifications about system-wide time changes.
I understand your concerns about that code, but please do not use timerfd 
as a sacrificial mule to fit something which IMO does not belong there.



- Davide


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