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Subject[PATCH 06/11] jump label: Tracepoint support for jump labels
From: Jason Baron <jbaron@redhat.com>

Make use of the jump label infrastructure for tracepoints.

Signed-off-by: Jason Baron <jbaron@redhat.com>
LKML-Reference: <a9ba2056e2c9cf332c3c300b577463ce66ff23a8.1284733808.git.jbaron@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
include/linux/tracepoint.h | 5 ++++-
kernel/tracepoint.c | 14 ++++++++++++--
2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 103d1b6..a4a90b6 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -17,6 +17,7 @@
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/rcupdate.h>
+#include <linux/jump_label.h>

struct module;
struct tracepoint;
@@ -145,7 +146,9 @@ static inline void tracepoint_update_probe_range(struct tracepoint *begin,
extern struct tracepoint __tracepoint_##name; \
static inline void trace_##name(proto) \
{ \
- if (unlikely(__tracepoint_##name.state)) \
+ JUMP_LABEL(&__tracepoint_##name.state, do_trace); \
+ return; \
+do_trace: \
__DO_TRACE(&__tracepoint_##name, \
TP_PROTO(data_proto), \
TP_ARGS(data_args)); \
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index c77f3ec..d6073a5 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[];
@@ -263,7 +264,13 @@ static void set_tracepoint(struct tracepoint_entry **entry,
* is used.
*/
rcu_assign_pointer(elem->funcs, (*entry)->funcs);
- elem->state = active;
+ if (!elem->state && active) {
+ enable_jump_label(&elem->state);
+ elem->state = active;
+ } else if (elem->state && !active) {
+ disable_jump_label(&elem->state);
+ elem->state = active;
+ }
}

/*
@@ -277,7 +284,10 @@ static void disable_tracepoint(struct tracepoint *elem)
if (elem->unregfunc && elem->state)
elem->unregfunc();

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

--
1.7.1



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