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Subject[PATCH 4/4] jump label - tracepoint implementation

Implement tracepoints if conditional on top of jump labels.

Signed-off-by: Jason Baron <jbaron@redhat.com>
---
include/linux/tracepoint.h | 31 +++++++++++++++++--------------
kernel/tracepoint.c | 10 ++++++++++
2 files changed, 27 insertions(+), 14 deletions(-)
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 63a3f7a..e7e2910 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, trace_label, __tracepoint_##name.state);\
+ __DO_TRACE(&__tracepoint_##name, \
+ TP_PROTO(proto), TP_ARGS(args)); \
+trace_label: \
+ return; \
+ } \
+ 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);\
}

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 9489a0a..e06bce8 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 +257,12 @@ static void set_tracepoint(struct tracepoint_entry **entry,
* is used.
*/
rcu_assign_pointer(elem->funcs, (*entry)->funcs);
+
+ if (!elem->state && active) {
+ enable_jump_label_locked(elem->name);
+ } else if (elem->state && !active)
+ disable_jump_label_locked(elem->name);
+
elem->state = active;
}

@@ -270,6 +277,9 @@ static void disable_tracepoint(struct tracepoint *elem)
if (elem->unregfunc && elem->state)
elem->unregfunc();

+ if (elem->state)
+ disable_jump_label_locked(elem->name);
+
elem->state = 0;
rcu_assign_pointer(elem->funcs, NULL);
}
--
1.6.2.5


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