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Subject[RFC PATCH 7/8] jump label v4 - tracepoint support
Make use of the jump label infrastructure for tracepoints.

Signed-off-by: Jason Baron <jbaron@redhat.com>
---
include/linux/tracepoint.h | 34 +++++++++++++++++++---------------
kernel/tracepoint.c | 8 ++++++++
2 files changed, 27 insertions(+), 15 deletions(-)
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index f59604e..c18b9c0 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -16,6 +16,7 @@

#include <linux/types.h>
#include <linux/rcupdate.h>
+#include <linux/jump_label.h>

struct module;
struct tracepoint;
@@ -63,20 +64,22 @@ struct tracepoint {
* not add unwanted padding between the beginning of the section and the
* structure. Force alignment to the same alignment as the section start.
*/
-#define DECLARE_TRACE(name, proto, args) \
- extern struct tracepoint __tracepoint_##name; \
- static inline void trace_##name(proto) \
- { \
- if (unlikely(__tracepoint_##name.state)) \
- __DO_TRACE(&__tracepoint_##name, \
- TP_PROTO(proto), TP_ARGS(args)); \
- } \
- static inline int register_trace_##name(void (*probe)(proto)) \
- { \
- return tracepoint_probe_register(#name, (void *)probe); \
- } \
- static inline int unregister_trace_##name(void (*probe)(proto)) \
- { \
+#define DECLARE_TRACE(name, proto, args) \
+ extern struct tracepoint __tracepoint_##name; \
+ static inline void trace_##name(proto) \
+ { \
+ JUMP_LABEL(name, do_trace, __tracepoint_##name.state); \
+ return; \
+do_trace: \
+ __DO_TRACE(&__tracepoint_##name, \
+ TP_PROTO(proto), TP_ARGS(args)); \
+ } \
+ static inline int register_trace_##name(void (*probe)(proto)) \
+ { \
+ return tracepoint_probe_register(#name, (void *)probe); \
+ } \
+ static inline int unregister_trace_##name(void (*probe)(proto)) \
+ { \
return tracepoint_probe_unregister(#name, (void *)probe);\
}

@@ -86,7 +89,8 @@ struct tracepoint {
__attribute__((section("__tracepoints_strings"))) = #name; \
struct tracepoint __tracepoint_##name \
__attribute__((section("__tracepoints"), aligned(32))) = \
- { __tpstrtab_##name, 0, reg, unreg, NULL }
+ { __tpstrtab_##name, 0, reg, unreg, NULL }; \
+ DEFINE_JUMP_LABEL(name);

#define DEFINE_TRACE(name) \
DEFINE_TRACE_FN(name, NULL, NULL);
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index cc89be5..8acced8 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -25,6 +25,7 @@
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/sched.h>
+#include <linux/jump_label.h>

extern struct tracepoint __start___tracepoints[];
extern struct tracepoint __stop___tracepoints[];
@@ -256,6 +257,10 @@ static void set_tracepoint(struct tracepoint_entry **entry,
* is used.
*/
rcu_assign_pointer(elem->funcs, (*entry)->funcs);
+ if (!elem->state && active)
+ enable_jump_label(elem->name);
+ if (elem->state && !active)
+ disable_jump_label(elem->name);
elem->state = active;
}

@@ -270,6 +275,9 @@ static void disable_tracepoint(struct tracepoint *elem)
if (elem->unregfunc && elem->state)
elem->unregfunc();

+ if (elem->state)
+ disable_jump_label(elem->name);
+
elem->state = 0;
rcu_assign_pointer(elem->funcs, NULL);
}
--
1.6.5.1


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