Re: [PATCH v3 1/4] rv/reactors: use context-sensitive lockdep wait type in rv_react()
From: Gabriele Monaco <gmonaco@redhat.com>
Date: 2026-08-12 12:34:10
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On Mon, 2026-08-10 at 01:10 +0800, wen.yang@linux.dev wrote:
From: Wen Yang <redacted>
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 <gmonaco@redhat.com>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 <gmonaco@redhat.com> Thanks, Gabriele
quoted hunk ↗ jump to hunk
Signed-off-by: Wen Yang <redacted> Cc: Thomas Weißschuh <redacted> --- 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);