[PATCH 1/3] rv/reactors: fix lockdep "Invalid wait context" in rv_react()

[wen . yang]

From: Wen Yang <wen.yang@xxxxxxxxx>

The DEFINE_WAIT_OVERRIDE_MAP() macro creates a lockdep map with
wait_type_inner = LD_WAIT_CONFIG, which inherits the outer context's
wait type.  When rv_react() is called from a LD_WAIT_FREE context
(e.g., a KUnit test with busy-wait), and the reactor callback triggers
a timer interrupt during the busy-loop, the interrupt exit path attempts
to schedule (preempt_schedule_irq -> __schedule -> rq->__lock), which is
LD_WAIT_SPIN.  Lockdep then reports:

    [ BUG: Invalid wait context ]
    context-{5:5}
    1 lock held by kunit_try_catch/209:
     #0: rv_react_map-wait-type-override at rv_react+0x9d/0xf0

The wait_type_override map allowed the outer LD_WAIT_FREE to propagate
inward, but scheduling from an interrupt is LD_WAIT_SPIN, violating the
constraint.

Fix by explicitly setting wait_type_inner = LD_WAIT_SPIN, which is the
tightest constraint rv_react() callbacks must satisfy: they may not
sleep (LD_WAIT_SLEEP) or use mutexes, but can use spinlocks and be
interrupted. This matches the documented LD_WAIT_FREE constraint.

Fixes: 69d8895cb9a9 ("rv: Add explicit lockdep context for reactors")
Signed-off-by: Wen Yang <wen.yang@xxxxxxxxx>
Cc: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
---
 kernel/trace/rv/rv_reactors.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/rv/rv_reactors.c b/kernel/trace/rv/rv_reactors.c
index 460af07f7aba..423f843bbd68 100644
--- a/kernel/trace/rv/rv_reactors.c
+++ b/kernel/trace/rv/rv_reactors.c
@@ -465,7 +465,13 @@ 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);
+#ifdef CONFIG_LOCKDEP
+	static struct lockdep_map rv_react_map = {
+		.name = "rv_react",
+		.wait_type_outer = LD_WAIT_FREE,
+		.wait_type_inner = LD_WAIT_SPIN,
+	};
+#endif
 	va_list args;
 
 	if (!rv_reacting_on() || !monitor->react)
-- 
2.25.1