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 any kernel where the task context has preemption
enabled (not just 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}
This series switches to a single LD_WAIT_SPIN override, hardens reactor
registration error handling, exports the registration helpers for
modules, and adds KUnit coverage.
Changes in v4:
- Patch 1: replace the context-sensitive two-map wait type with a
single LD_WAIT_SPIN override, and document the constraint.
- Patch 4: use a plain int instead of atomic_t for the test counter,
trim redundant comments.
v3: https://lore.kernel.org/lkml/[email protected]/
v2: https://lore.kernel.org/lkml/[email protected]/
v1: https://lore.kernel.org/lkml/[email protected]/
Wen Yang (4):
rv/reactors: use LD_WAIT_SPIN as the reactor lockdep wait type
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
Documentation/trace/rv/monitor_synthesis.rst | 20 ++++
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 | 8 +-
kernel/trace/rv/rv_reactors_kunit.c | 105 +++++++++++++++++++
7 files changed, 147 insertions(+), 5 deletions(-)
create mode 100644 kernel/trace/rv/rv_reactors_kunit.c
base-commit: 785095112f4198de49760552374f364043c8dbdf
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2.25.1
