2 files changed, 34 insertions, 0 deletions

diff --git a/Documentation/trace/tracepoints.txt b/Documentation/trace/tracepoints.txt
index 6b018b53177a..a3efac621c5a 100644
--- a/Documentation/trace/tracepoints.txt
+++ b/Documentation/trace/tracepoints.txt
@@ -115,6 +115,30 @@ If the tracepoint has to be used in kernel modules, an
 EXPORT_TRACEPOINT_SYMBOL_GPL() or EXPORT_TRACEPOINT_SYMBOL() can be
 used to export the defined tracepoints.
 
+If you need to do a bit of work for a tracepoint parameter, and
+that work is only used for the tracepoint, that work can be encapsulated
+within an if statement with the following:
+
+        if (trace_foo_bar_enabled()) {
+                int i;
+                int tot = 0;
+
+                for (i = 0; i < count; i++)
+                        tot += calculate_nuggets();
+
+                trace_foo_bar(tot);
+        }
+
+All trace_<tracepoint>() calls have a matching trace_<tracepoint>_enabled()
+function defined that returns true if the tracepoint is enabled and
+false otherwise. The trace_<tracepoint>() should always be within the
+block of the if (trace_<tracepoint>_enabled()) to prevent races between
+the tracepoint being enabled and the check being seen.
+
+The advantage of using the trace_<tracepoint>_enabled() is that it uses
+the static_key of the tracepoint to allow the if statement to be implemented
+with jump labels and avoid conditional branches.
+
 Note: The convenience macro TRACE_EVENT provides an alternative way to
       define tracepoints. Check http://lwn.net/Articles/379903,
       http://lwn.net/Articles/381064 and http://lwn.net/Articles/383362
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 9d30ee469c2a..2e2a5f7717e5 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -185,6 +185,11 @@ extern void syscall_unregfunc(void);
         static inline void                                              \
         check_trace_callback_type_##name(void (*cb)(data_proto))        \
         {                                                               \
+        }                                                               \
+        static inline bool                                              \
+        trace_##name##_enabled(void)                                    \
+        {                                                               \
+                return static_key_false(&__tracepoint_##name.key);      \
         }
 
 /*
@@ -230,6 +235,11 @@ extern void syscall_unregfunc(void);
         }                                                               \
         static inline void check_trace_callback_type_##name(void (*cb)(data_proto)) \
         {                                                               \
+        }                                                               \
+        static inline bool                                              \
+        trace_##name##_enabled(void)                                    \
+        {                                                               \
+                return false;                                           \
         }
 
 #define DEFINE_TRACE_FN(name, reg, unreg)