From: Wen Yang <[email protected]>
We occasionally hit a lockdep "Invalid wait context" warning in
production when a reactor callback is preempted by a timer interrupt.
On interrupt exit the scheduler takes rq->__lock (LD_WAIT_SPIN) while
rv_react() still holds its wait-type-override map, which declared
LD_WAIT_FREE. On a preemptible kernel (e.g. CONFIG_PREEMPT_RT) this
triggers a spurious lockdep report:
[ BUG: Invalid wait context ]
1 lock held by kunit_try_catch/209:
#0: (rv_react_map-wait-type-override){+.+.}-{1:1}
kunit_try_catch/209 is trying to lock:
ffff8a743ed3e8a0 (&rq->__lock){-...}-{2:2}
Changes in v2:
- Use a context-sensitive override map: LD_WAIT_SPIN in preemptible
contexts, LD_WAIT_FREE in NMI/hardirq where the scheduler cannot run
(patch 1).
- Merge the v1 printk/panic test files into one generic rv_reactors_kunit
covering registration and dispatch, as the v1 tests were mostly not
reactor-specific (patches 2-4).
- Export rv_register_reactor()/rv_unregister_reactor() so the tristate
KUnit module can link against them (patch 3).
- Propagate rv_register_reactor() errors from the built-in reactor init
functions instead of silently ignoring them (patch 2).
- KUnit tests are tristate (usable with CONFIG_KUNIT=m) and verify the
callback is actually invoked (atomic counter), the exact -EINVAL on
duplicate registration, and use mdelay(5) to exercise the lockdep
context under load. A teardown action unregisters the test reactor
even if a test aborts.
Patch 1 fixes the lockdep warning. Patches 2-3 make the registration
API usable by the test module and propagate its errors. Patch 4 adds
the KUnit tests.
Tested with CONFIG_PROVE_LOCKING=y and CONFIG_KUNIT=y.
Wen Yang (4):
rv/reactors: use context-sensitive lockdep wait type in rv_react()
rv/reactors: propagate rv_register_reactor() error from reactor init
rv/reactors: export rv_register_reactor() and rv_unregister_reactor()
rv/reactors: add KUnit tests for reactor registration and dispatch
kernel/trace/rv/Kconfig | 12 +++
kernel/trace/rv/Makefile | 1 +
kernel/trace/rv/reactor_panic.c | 3 +-
kernel/trace/rv/reactor_printk.c | 3 +-
kernel/trace/rv/rv_reactors.c | 19 +++-
kernel/trace/rv/rv_reactors_kunit.c | 143 ++++++++++++++++++++++++++++
6 files changed, 172 insertions(+), 9 deletions(-)
create mode 100644 kernel/trace/rv/rv_reactors_kunit.c
base-commit: 984b5a36fd12d1849511a45fda32036fe2b0d004
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2.25.1
