[PATCH v6 0/4] rv/reactors: fix lockdep warning and add tests

[wen.yang@linux.dev]

From: Wen Yang <wen.yang@linux.dev>

We occasionally hit a lockdep "Invalid wait context" warning 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 fixes the wait type (patch 1), makes reactor registration
failures propagate (patch 2), adds support for module-based
reactors (patch 3), and adds KUnit/kselftest coverage (patch 4-5).

Changes in v5:
- Patch 1: Fix typo. Functional code unchanged.
- Patch 2: Unchanged.
- Patch 3: Only exported the registration helpers as v4.
- Patch 4: Fix typo. Functional code unchanged.

v5: https://lore.kernel.org/lkml/cover.1788705281.git.wen.yang@linux.dev/
v4: https://lore.kernel.org/lkml/cover.1787854397.git.wen.yang@linux.dev/
v3: https://lore.kernel.org/lkml/cover.1786294920.git.wen.yang@linux.dev/
v2: https://lore.kernel.org/lkml/cover.1785695669.git.wen.yang@linux.dev/
v1: https://lore.kernel.org/lkml/cover.1781541556.git.wen.yang@linux.dev/

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

 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       |  12 ++-
 kernel/trace/rv/rv_reactors_kunit.c | 111 ++++++++++++++++++++++++++++
 6 files changed, 137 insertions(+), 5 deletions(-)
 create mode 100644 kernel/trace/rv/rv_reactors_kunit.c

-- 
2.25.1