On Mon, 2026-08-10 at 01:10 +0800, [email protected] wrote: > From: Wen Yang <[email protected]> > > Reactors must not explicitly take locks, so they should comply with > LD_WAIT_FREE. However, reactor callbacks can run with preemption > enabled on any kernel (not just PREEMPT_RT). If a timer interrupt > fires during the callback, the interrupt exit path schedules and > acquires rq->__lock (LD_WAIT_SPIN) while the lockdep override map that > declared LD_WAIT_FREE is still held, triggering a spurious > "Invalid wait context" warning: > > [ BUG: Invalid wait context ] > context-{5:5} > 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} > > Fixes: 69d8895cb9a9 ("rv: Add explicit lockdep context for reactors") > Suggested-by: Gabriele Monaco <[email protected]>
You came up with the idea, I at most suggested how I'd like it worded in the comment. Anyway, I'd appreciate comments/acks from the other folks in the loop, but from my side this looks good. Reviewed-by: Gabriele Monaco <[email protected]> Thanks, Gabriele > Signed-off-by: Wen Yang <[email protected]> > Cc: Thomas Weißschuh <[email protected]> > --- > kernel/trace/rv/rv_reactors.c | 20 +++++++++++++++----- > 1 file changed, 15 insertions(+), 5 deletions(-) > > diff --git a/kernel/trace/rv/rv_reactors.c b/kernel/trace/rv/rv_reactors.c > index 2f5fc8d18dea..5830229210e8 100644 > --- a/kernel/trace/rv/rv_reactors.c > +++ b/kernel/trace/rv/rv_reactors.c > @@ -465,18 +465,28 @@ int init_rv_reactors(struct dentry *root_dir) > > void rv_react(struct rv_monitor *monitor, const char *msg, ...) > { > - static DEFINE_WAIT_OVERRIDE_MAP(rv_react_map, LD_WAIT_FREE); > + /* > + * Reactors must not explicitly take locks, so they should be > + * LD_WAIT_FREE. However, reactor callbacks can run with preemption > + * enabled, meaning the preempting code (e.g. the scheduler taking > + * rq->__lock at LD_WAIT_SPIN) may violate that constraint. Use > + * LD_WAIT_SPIN in preemptible contexts to avoid false-positive > lockdep > + * reports; keep LD_WAIT_FREE in NMI/hardirq where preemption is > + * disabled and the scheduler cannot run. > + */ > + static DEFINE_WAIT_OVERRIDE_MAP(rv_react_map, LD_WAIT_SPIN); > + static DEFINE_WAIT_OVERRIDE_MAP(rv_react_map_atomic, LD_WAIT_FREE); > + struct lockdep_map * __maybe_unused map; > va_list args; > > if (!rv_reacting_on() || !monitor->react) > return; > > + map = (in_nmi() || in_hardirq()) ? &rv_react_map_atomic : > &rv_react_map; > va_start(args, msg); > - > - lock_map_acquire_try(&rv_react_map); > + lock_map_acquire_try(map); > monitor->react(msg, args); > - lock_map_release(&rv_react_map); > - > + lock_map_release(map); > va_end(args); > } > EXPORT_SYMBOL_GPL(rv_react);
