From: Wen Yang <[email protected]>
The single DEFINE_WAIT_OVERRIDE_MAP(rv_react_map, LD_WAIT_FREE) in
rv_react() declares wait_type_inner = LD_WAIT_FREE for every execution
context. In a preemptible context (e.g. CONFIG_PREEMPT_RT or a KUnit
test running on a task), a timer interrupt can fire during a reactor
callback; the interrupt exit path then schedules and acquires rq->__lock
(LD_WAIT_SPIN) while the override map is still held. Since the map
declares the context to be wait-free, lockdep reports 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}
Use two lockdep override maps, selected by execution context:
- Preemptible context (task, softirq, PREEMPT_RT irq thread): the
scheduler may preempt, so use LD_WAIT_SPIN, the tightest wait type
the scheduler itself uses, to suppress the spurious warning.
- NMI/hardirq context: preemption is disabled and the scheduler cannot
run, so the false positive cannot arise. Keep LD_WAIT_FREE here to
preserve the original constraint that reactors must not take raw
spinlocks in atomic context.
Fixes: 69d8895cb9a9 ("rv: Add explicit lockdep context for reactors")
Signed-off-by: Wen Yang <[email protected]>
Cc: Thomas Weißschuh <[email protected]>
---
kernel/trace/rv/rv_reactors.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/kernel/trace/rv/rv_reactors.c b/kernel/trace/rv/rv_reactors.c
index 2f5fc8d18dea..cd571b1649f5 100644
--- a/kernel/trace/rv/rv_reactors.c
+++ b/kernel/trace/rv/rv_reactors.c
@@ -465,18 +465,25 @@ 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);
+ /*
+ * A reactor callback can be preempted; the scheduler then takes
+ * rq->__lock (LD_WAIT_SPIN). Advertise that in preemptible contexts
+ * to avoid a spurious lockdep report, and keep LD_WAIT_FREE in atomic
+ * ones where 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);
--
2.25.1
