Re: [for-next][PATCH 04/15] tracepoint: Add lockdep rcu_is_watching() check to trace_##name##_enabled()

[Steven Rostedt <rostedt@kernel.org>]

On Wed, 1 Jul 2026 11:24:31 +0200
Geert Uytterhoeven <geert@linux-m68k.org> wrote:

> Thanks, it does not trigger with the commit reverted and the "echo 1 > ...".

Ah found the issue;

#define trace(point, args)                                      \
        do {                                                    \
                if (trace_##point##_enabled()) {                \
                        bool exit_rcu = false;                  \
                        if (in_nmi())                           \
                                break;                          \
                        if (!IS_ENABLED(CONFIG_TINY_RCU) &&     \
                            is_idle_task(current)) {            \
                                ct_irq_enter();                 \
                                exit_rcu = true;                \
                        }                                       \
                        trace_##point(args);                    \
                        if (exit_rcu)                           \
                                ct_irq_exit();                  \
                }                                               \
        } while (0)
#endif

The code within the enabled() call checks if RCU is watching, and if
not, it makes it watch. So yeah, this is a special case.

The following patch should fix the issue:

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 4a0c36f40fe2..e0d838c9ce93 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -292,13 +292,18 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 	{								\
 	}								\
 	static inline bool						\
+	__trace_##name##_enabled(void)					\
+	{								\
+		return static_branch_unlikely(&__tracepoint_##name.key);\
+	}								\
+	static inline bool						\
 	trace_##name##_enabled(void)					\
 	{								\
 		if (IS_ENABLED(CONFIG_LOCKDEP)) {			\
 			WARN_ONCE(!rcu_is_watching(),			\
 				  "RCU not watching for tracepoint");	\
 		}							\
-		return static_branch_unlikely(&__tracepoint_##name.key);\
+		return __trace_##name##_enabled();			\
 	}
 
 #define __DECLARE_TRACE(name, proto, args, cond, data_proto)			\
@@ -457,6 +462,11 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 	{								\
 	}								\
 	static inline bool						\
+	__trace_##name##_enabled(void)					\
+	{								\
+		return false;						\
+	}								\
+	static inline bool						\
 	trace_##name##_enabled(void)					\
 	{								\
 		return false;						\
diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c
index 0c42b15c3800..b63e3558948f 100644
--- a/kernel/trace/trace_preemptirq.c
+++ b/kernel/trace/trace_preemptirq.c
@@ -30,7 +30,7 @@
 #else
 #define trace(point, args)					\
 	do {							\
-		if (trace_##point##_enabled()) {		\
+		if (__trace_##point##_enabled()) {		\
 			bool exit_rcu = false;			\
 			if (in_nmi())				\
 				break;				\