Add cgroup:cgroup_freeze and cgroup:cgroup_unfreeze events,
which are using the existing cgroup tracing infrastructure.
Add the cgroup_event event class, which is similar to the cgroup
class, but contains an additional integer field to store a new
value (the level field is dropped).
Also add two tracing events: cgroup_notify_populated and
cgroup_notify_frozen, which are raised in a generic way using
the TRACE_CGROUP_PATH() macro.
This allows to trace cgroup state transitions and is generally
helpful for debugging the cgroup freezer code.
Change-Id: I6c3f9efafc4d4a7c89332696f7e117ba8e257ade
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
ef5da0e654