notifiers: add tracepoints to the notifiers infrastructure

Currently there is no way to show the callback names for registered,
unregistered or executed notifiers. This is very useful for debug
purposes, hence add this functionality here in the form of notifiers'
tracepoints, one per operation.

[[email protected]: coding-style cleanups]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Guilherme G. Piccoli <[email protected]>
Cc: Arjan van de Ven <[email protected]>
Cc: Michael Kelley <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Xiaoming Ni <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Cong Wang <[email protected]>
Cc: Dmitry Osipenko <[email protected]>
Cc: Guilherme G. Piccoli <[email protected]>
Cc: Guilherme G. Piccoli <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Rafael J. Wysocki <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Cc: Valentin Schneider <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
2 files changed