linux-kernel - Re: [PATCH] [RFCv2] notify userspace about time changes

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Message-ID: <1282211446.1926.4609.camel@laptop>
Date:	Thu, 19 Aug 2010 11:50:46 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Alexander Shishkin <virtuoso@...nd.org>, lkml@...r.kernel.org,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <johnstul@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Jon Hunter <jon-hunter@...com>, Ingo Molnar <mingo@...e.hu>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	David Howells <dhowells@...hat.com>,
	Avi Kivity <avi@...hat.com>, John Kacur <jkacur@...hat.com>,
	Chris Friesen <chris.friesen@...band.com>,
	Kay Sievers <kay.sievers@...y.org>, Greg KH <gregkh@...e.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [RFCv2] notify userspace about time changes

On Wed, 2010-08-18 at 16:53 -0700, Andrew Morton wrote:
> 
> 
> Such applications might be better served via a wake-me-at-this-time
> syscall instead of a sleep-me-for-this-long syscall.  Although such a
> thing is less general.
> 
We have timer_create(.clockid = CLOCK_REALTIME) for such things, no?

> > +                  fd = open("/sys/kernel/time_notify", O_WRONLY);
> > +                  fdprintf(fd, "%d 1 0 1 1", efd);
> 
> why not
> 
>                 sys_time_notify(efd, 1, 0, 1, 1);

And then there is the /dev/time proposal from Plan9:

  http://lkml.org/lkml/2009/3/11/363

Their proposal was to add a poll() method to the device which would wake
on every change in time.
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