events: Ensure that timers are updated without requiring read() call

The event tracing infrastructure exposes two timers which should be updated
each time the value of the counter is updated.  Currently, these counters are
only updated when userspace calls read() on the fd associated with an event.
This means that counters which are read via the mmap'd page exclusively never
have their timers updated.  This patch adds ensures that the timers are updated
each time the values in the mmap'd page are updated.

Signed-off-by: Eric B Munson <emunson@mgebm.net>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1308932786-5111-1-git-send-email-emunson@mgebm.net


Signed-off-by: Ingo Molnar <mingo@elte.hu>