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
hwpmc: drain a process-mode PMC's runcount when a live target detaches
A process-mode PMC's runcount tracks how many CPUs currently have it
loaded in hardware. It is decremented only by the context-switch-out
and process-exit reclaim paths, both of which the scheduler invokes
only for processes flagged P_HWPMC. Detaching a target that still has
the PMC live in hardware dropped the target and cleared P_HWPMC without
taking the PMC off the hardware or dropping the runcount reference, so
the reference leaked. A subsequent release then spun in
pmc_wait_for_pmc_idle() forever waiting for the runcount to reach zero:
on an INVARIANTS kernel this panics ("waiting too long for pmc to be
free"), otherwise it is an unkillable loop holding the hwpmc lock. Any
process able to allocate a PMC can trigger this by attaching a counting
PMC to itself and detaching it before releasing.
Take the PMC off the hardware and drop the runcount reference as part
of detaching, before P_HWPMC is cleared: reclaim it from the detaching
thread's own CPU directly, and, when the detach removes the PMC's last
target, wait for any references held by the target's other threads to
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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
hwpmc: handle counter wraparound for process-mode counting PMCs
The accumulated count of a process-mode counting PMC is kept in a
64-bit software counter and seeded into the hardware counter at every
context switch in. Hardware counters are narrower than that - each
PMC class discovers and records its own counter width, e.g. 48 bits
on current x86 (queried from CPUID on Intel, architectural on AMD) -
so once the accumulated count approaches the end of the hardware
counter range, the counter wraps during a time slice and the value
read back at switch out is smaller than the value seeded. The
increment was computed assuming a full 64-bit counter: on INVARIANTS
kernels a long enough counting run panics with "negative increment"
the moment the accumulated count first crosses the hardware counter
range, and on other kernels the totals silently lose a full counter
range per wrap.
Compute the increment modulo the per-class hardware counter width
instead, in both places that accumulate switch-out deltas.
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ports-mgmt/pkg: update to 2.8.0
Major Changes:
==============
Database & performance
- better read/write concurrency on the local DB
- Schema bumped to v42: 15 redundant single-column indexes dropped, flavors VIEW added, shlib_id indexes added
- Read-only databases opened with SQLITE_OPEN_READONLY, falling back to immutable=1
- Binary repositories: 16K pages and synchronous=OFF during bulk catalog updates
- Implicit SQL-89 JOINs converted to explicit JOIN syntax, several queries optimized
- Some database concurrency issues fixed
New features
- pkg-checksum(8): new command to generate and validate checksums
- Blake2b used everywhere possible for checksums; repositories use blake2 instead of sha256
- rwhich: file tracking and search for remote repositories (requires repositories to be built with -l)
- pkg delete -G/--exclude-glob: exclude packages by glob pattern
- Repositories: enable/disable/reset support
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apei: Fix i386 build over bus read, write function
bus_{read,write}_8 are macro wrappers around the corresponding bus_space
functions in sys/bus.h, so implementing bus_{read,write}_8 won't work.
Implement the underlying bus_space function instead.
Reviewed by: jrtc27, rlibby
Fixes: 9313f6b01485
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D58301
