Re: [PATCH] timerfd: add TFD_NOTIFY_CLOCK_SET to watch for clock changes

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