On Fri, 2012-08-17 at 00:02 +1000, Michael Ellerman wrote:
You do want to guarantee that the task will always be subject to the
breakpoint, even if it moves cpus. So is there any way to guarantee that
other than reserving a breakpoint slot on every cpu ahead of time?=20
That's not how regular perf works.. regular perf can overload hw
resources at will and stuff is strictly per-cpu.
So the regular perf record has perf_event_attr::inherit enabled by
default, this will result in it creating a per-task-per-cpu event for
each cpu and this will succeed because there's no strict reservation to
avoid/detect starvation against perf_event_attr::pinned events.
For regular (!pinned) events, we'll RR the created events on the
available hardware resources.
HWBP does things completely different and reserves a slot over all CPUs
for everything, thus stuff completely falls apart.