timekeeping: Add the new CLOCK_MONOTONIC_ACTIVE clock

timekeeping: Add the new CLOCK_MONOTONIC_ACTIVE clock

The planned change to unify the behaviour of the MONOTONIC and BOOTTIME
clocks vs. suspend removes the ability to retrieve the active
non-suspended time of a system.

Provide a new CLOCK_MONOTONIC_ACTIVE clock which returns the active
non-suspended time of the system via clock_gettime().

This preserves the old behaviour of CLOCK_MONOTONIC before the
BOOTTIME/MONOTONIC unification.

This new clock also allows applications to detect programmatically that
the MONOTONIC and BOOTTIME clocks are identical.

Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Dmitry Torokhov <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Kevin Easton <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mark Salyzyn <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Steven Rostedt <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>