From mboxrd@z Thu Jan  1 00:00:00 1970
From: john stultz <johnstul-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH] timerfd: add TFD_NOTIFY_CLOCK_SET to watch for clock
 changes
Date: Wed, 01 Dec 2010 16:14:27 -0800
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Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
	Alexander Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>,
	Greg Kroah-Hartman <gregkh-l3A5Bk7waGM@public.gmane.org>,
	Feng Tang <feng.tang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Michael Tokarev <mjt-XAri/EZa3C4vJsYlp49lxw@public.gmane.org>,
	Marcelo Tosatti <mtosatti-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Chris Friesen <chris.friesen-b7o/lNNmKxtBDgjK7y7TUQ@public.gmane.org>,
	Kay Sievers <kay.sievers-tD+1rO4QERM@public.gmane.org>,
	"Kirill A. Shutemov" <kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>,
	Artem Bityutskiy <dedekind1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Davide Libenzi <davidel-AhlLAIvw+VEjIGhXcJzhZg@public.gmane.org>,
	Lennart Poettering <mzxreary-uLTowLwuiw4b1SvskN2V4Q@public.gmane.org>,
	linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
To: Alexander Shishkin <virtuoso-0lOfPCoBze7YtjvyW6yDsg@public.gmane.org>
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On Wed, 2010-12-01 at 03:39 +0200, Alexander Shishkin wrote:
> To use this notification functionality, user has to call timerfd_settime()
> with TFD_NOTIFY_CLOCK_SET flag. After this CLOCK_REALTIME timers will
> read as the number of times the wall clock has been set since last read
> and poll every time the wall clock is set; CLOCK_MONOTONIC timers will
> behave likewise, but in the event of the clock being updated upon resuming
> from suspend. For both CLOCK_REALTIME and CLOCK_MONOTONIC timers with
> TFD_NOTIFY_CLOCK_SET flag set, a call to timerfd_gettime() will return
> current wall clock in it_value.

The CLOCK_MONOTONIC flag on resume worries me a bit (since
CLOCK_MONOTONIC isn't adjusted on resume).

What is the use case there?

thanks
-john