[PATCH] tracepoints: Implement it with dynamic functions

[Steven Rostedt (VMware)]

Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
 include/linux/tracepoint-defs.h |  4 +++-
 include/linux/tracepoint.h      | 24 ++++++++++++------------
 kernel/tracepoint.c             |  8 ++++----
 3 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
index 8013fc442964..ae16672bea61 100644
--- a/include/linux/tracepoint-defs.h
+++ b/include/linux/tracepoint-defs.h
@@ -11,6 +11,8 @@
 #include <linux/atomic.h>
 #include <linux/static_key.h>
 
+struct static_call_key;
+
 struct trace_print_flags {
 	unsigned long		mask;
 	const char		*name;
@@ -30,7 +32,7 @@ struct tracepoint_func {
 struct tracepoint {
 	const char *name;		/* Tracepoint name */
 	struct static_key key;
-	void **function_ptr;
+	struct static_call_key *static_call_key;
 	void *iterator;
 	int (*regfunc)(void);
 	void (*unregfunc)(void);
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index b60d547c44ba..e0d787a7e68b 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -21,6 +21,7 @@
 #include <linux/cpumask.h>
 #include <linux/rcupdate.h>
 #include <linux/tracepoint-defs.h>
+#include <linux/static_call.h>
 
 struct module;
 struct tracepoint;
@@ -191,8 +192,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 			rcu_dereference_raw((&__tracepoint_##name)->funcs); \
 		if (it_func_ptr) {					\
 			__data = (it_func_ptr)->data;			\
-			/* printk("%pS\n", __tp_func_##name); */		\
-			__tp_func_##name(args);				\
+			static_call(__tp_func_##name, args);		\
 		}							\
 									\
 		if (rcuidle) {						\
@@ -230,8 +230,8 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
  * poking RCU a bit.
  */
 #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
-	extern void __tracepoint_iter_##name(data_proto);		\
-	extern void (*__tp_func_##name)(data_proto);			\
+	extern int __tracepoint_iter_##name(data_proto);		\
+	DECLARE_STATIC_CALL(__tp_func_##name, __tracepoint_iter_##name); \
 	extern struct tracepoint __tracepoint_##name;			\
 	static inline void trace_##name(proto)				\
 	{								\
@@ -285,16 +285,15 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 #define DEFINE_TRACE_FN(name, reg, unreg, proto, args)			\
 	static const char __tpstrtab_##name[]				\
 	__attribute__((section("__tracepoints_strings"))) = #name;	\
-	void __tracepoint_iter_##name(void *__data, proto);		\
-	void (*__tp_func_##name)(void *__data, proto) =			\
-		__tracepoint_iter_##name;				\
+	int __tracepoint_iter_##name(void *__data, proto);		\
+	extern struct static_call_key __tp_func_##name;			\
 	struct tracepoint __tracepoint_##name				\
 	__attribute__((section("__tracepoints"), used)) =		\
 		{ __tpstrtab_##name, STATIC_KEY_INIT_FALSE,		\
-		  (void **)&__tp_func_##name, __tracepoint_iter_##name,	\
+		  &__tp_func_##name, __tracepoint_iter_##name,		\
 		  reg, unreg, NULL };					\
 	__TRACEPOINT_ENTRY(name);					\
-	void __tracepoint_iter_##name(void *__data, proto)		\
+	int __tracepoint_iter_##name(void *__data, proto)		\
 	{								\
 		struct tracepoint_func *it_func_ptr;			\
 		void *it_func;						\
@@ -307,17 +306,18 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 			((void(*)(void *, proto))(it_func))(__data, args); \
 		} while ((++it_func_ptr)->func);			\
 		return 0;						\
-	}
+	}								\
+	DEFINE_STATIC_CALL(__tp_func_##name, __tracepoint_iter_##name);
 
 #define DEFINE_TRACE(name, proto, args)		\
 	DEFINE_TRACE_FN(name, NULL, NULL, PARAMS(proto), PARAMS(args));
 
 #define EXPORT_TRACEPOINT_SYMBOL_GPL(name)				\
 	EXPORT_SYMBOL_GPL(__tracepoint_##name);				\
-	EXPORT_SYMBOL_GPL(__tp_func_##name)
+	EXPORT_STATIC_CALL_GPL(__tp_func_##name)
 #define EXPORT_TRACEPOINT_SYMBOL(name)					\
 	EXPORT_SYMBOL(__tracepoint_##name);				\
-	EXPORT_SYMBOL(__tp_func_##name)
+	EXPORT_STATIC_CALL(__tp_func_##name)
 
 
 #else /* !TRACEPOINTS_ENABLED */
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 7e1f34edd1d7..4105bdd872f9 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -271,10 +271,10 @@ static int tracepoint_add_func(struct tracepoint *tp,
 
 	if (probes == 1) {
 		printk("make direct call to %pS\n", tp_funcs->func);
-		*tp->function_ptr = tp_funcs->func;
+		__static_call_update(tp->static_call_key, tp_funcs->func);
 	} else {
 		printk("[%d] make call to iterator %pS\n", probes, tp->iterator);
-		*tp->function_ptr = tp->iterator;
+		__static_call_update(tp->static_call_key, tp->iterator);
 	}
 
 	release_probes(old);
@@ -312,10 +312,10 @@ static int tracepoint_remove_func(struct tracepoint *tp,
 
 	if (probes_left == 1) {
 		printk("make direct call to %pS\n", tp_funcs->func);
-		*tp->function_ptr = tp_funcs->func;
+		__static_call_update(tp->static_call_key, tp_funcs->func);
 	} else {
 		printk("[%d] make call to iterator %pS\n", probes_left, tp->iterator);
-		*tp->function_ptr = tp->iterator;
+		__static_call_update(tp->static_call_key, tp->iterator);
 	}
 
 	rcu_assign_pointer(tp->funcs, tp_funcs);
-- 
2.19.1


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