aboutsummaryrefslogtreecommitdiff
path: root/include/linux/tracepoint.h
diff options
context:
space:
mode:
authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2014-05-06 09:26:30 -0400
committerSteven Rostedt <rostedt@goodmis.org>2014-05-07 12:10:51 -0400
commit7c65bbc7dcface00b295bbd18bce82fe1db3d633 (patch)
tree4e5cd0710e3c533831eb673f8feeb46a911a9f09 /include/linux/tracepoint.h
parentbdffd893a0e9c431304142d12d9a0a21d365c502 (diff)
downloadlinux-linaro-stable-7c65bbc7dcface00b295bbd18bce82fe1db3d633.tar.gz
tracing: Add trace_<tracepoint>_enabled() function
There are some code paths in the kernel that need to do some preparations before it calls a tracepoint. As that code is worthless overhead when the tracepoint is not enabled, it would be prudent to have that code only run when the tracepoint is active. To accomplish this, all tracepoints now get a static inline function called "trace_<tracepoint-name>_enabled()" which returns true when the tracepoint is enabled and false otherwise. As an added bonus, that function uses the static_key of the tracepoint such that no branch is needed. if (trace_mytracepoint_enabled()) { arg = process_tp_arg(); trace_mytracepoint(arg); } Will keep the "process_tp_arg()" (which may be expensive to run) from being executed when the tracepoint isn't enabled. It's best to encapsulate the tracepoint itself in the if statement just to keep races. For example, if you had: if (trace_mytracepoint_enabled()) arg = process_tp_arg(); trace_mytracepoint(arg); There's a chance that the tracepoint could be enabled just after the if statement, and arg will be undefined when calling the tracepoint. Link: http://lkml.kernel.org/r/20140506094407.507b6435@gandalf.local.home Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include/linux/tracepoint.h')
-rw-r--r--include/linux/tracepoint.h10
1 files changed, 10 insertions, 0 deletions
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)