hwpmc: add regression tests for detaching a live process-mode PMC

Attach a process-mode counting PMC to the current process, start it,
then detach and release it while it is still loaded on the hard

hwpmc: add regression tests for detaching a live process-mode PMC

Attach a process-mode counting PMC to the current process, start it,
then detach and release it while it is still loaded on the hardware -
the case that previously leaked the PMC's runcount reference and
wedged pmc_wait_for_pmc_idle() at release. A second case does the same
from a multi-threaded process so the sibling threads' references have
to be drained too.

The tests need an allocatable process-mode counting event and skip
where none is available (hwpmc(4) not loaded, or a VM without a vPMU).

Reviewed by: adrian
MFC after: 2 weeks
Assisted-by: Claude Code (Fable 5)
Differential Revision: https://reviews.freebsd.org/D58343

show more ...

hwpmc: add regression tests for counting-PMC counter wraparound

Exercise a process-mode counting PMC whose accumulated count crosses,
or already exceeds, the range of the underlying hardware counter

hwpmc: add regression tests for counting-PMC counter wraparound

Exercise a process-mode counting PMC whose accumulated count crosses,
or already exceeds, the range of the underlying hardware counter.
Before the previous commit, the first context switch after the
hardware counter wrapped panicked INVARIANTS kernels with "negative
increment" and silently corrupted the accumulated count on other
kernels.

The tests need a hardware counting event backed by a counter narrower
than 64 bits and skip where none is available (hwpmc(4) not loaded,
or a VM without a vPMU).

Reviewed by: adrian
MFC after: 2 weeks
Assisted-by: Claude Code (Fable 5)
Differential Revision: https://reviews.freebsd.org/D58341

show more ...