On Tue, Mar 29, 2016 at 11:57:00AM -0400, Steven Rostedt wrote:

Hmm, I probably could add tracing infrastructure that would let us
extend existing tracepoints. That is, without modifying sched_switch,
we could add a new tracepoint that when enabled, would attach itself to
the sched_switch tracepoint and record different information. Like a
special sched_switch_deadline tracepoint, that would record the existing
runtime,deadline and period for deadline tasks. It wont add more
tracepoints into the core scheduler, but use the existing one.

Urgh; maybe. But I would would not want the new thing to be called
_deadline, maybe _v{n} id anything and have a KERN_WARNING emitted when
people enable the old one.

Ideally we'd rename the old one, but I suspect even that would break
stuff :/