[PATCH 01/15] tracepoint: Add trace_invoke_##name() API

Vineeth Pillai (Google)
2026-03-12T15:05:39Z

Add trace_invoke_##name() as a companion to trace_##name(). When a
caller already guards a tracepoint with an explicit enabled check:

if (trace_foo_enabled() && cond)
trace_foo(args);

trace_foo() internally repeats the static_branch_unlikely() test, which
the compiler cannot fold since static branches are patched binary
instructions. This results in two static-branch evaluations for every
guarded call site.

trace_invoke_##name() calls __do_trace_##name() directly, skipping the
redundant static-branch re-check. This avoids leaking the internal
__do_trace_##name() symbol into call sites while still eliminating the
double evaluation:

if (trace_foo_enabled() && cond)
trace_invoke_foo(args); /* calls __do_trace_foo() directly */

Three locations are updated:
- __DECLARE_TRACE: invoke form omits static_branch_unlikely, retains
the LOCKDEP RCU-watching assertion.
- __DECLARE_TRACE_SYSCALL: same, plus retains might_fault().
- !TRACEPOINTS_ENABLED stub: empty no-op so callers compile cleanly
when tracepoints are compiled out.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Vineeth Pillai (Google) <vineeth@bitbyteword.org>
Assisted-by: Claude:claude-sonnet-4-6
---
include/linux/tracepoint.h | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 22ca1c8b54f32..07219316a8e14 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -294,6 +294,10 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
WARN_ONCE(!rcu_is_watching(), \
"RCU not watching for tracepoint"); \
} \
+ } \
+ static inline void trace_invoke_##name(proto) \
+ { \
+ __do_trace_##name(args); \
}

#define __DECLARE_TRACE_SYSCALL(name, proto, args, data_proto) \
@@ -313,6 +317,11 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
WARN_ONCE(!rcu_is_watching(), \
"RCU not watching for tracepoint"); \
} \
+ } \
+ static inline void trace_invoke_##name(proto) \
+ { \
+ might_fault(); \
+ __do_trace_##name(args); \
}

/*
@@ -398,6 +407,8 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
#define __DECLARE_TRACE_COMMON(name, proto, args, data_proto) \
static inline void trace_##name(proto) \
{ } \
+ static inline void trace_invoke_##name(proto) \
+ { } \
static inline int \
register_trace_##name(void (*probe)(data_proto), \
void *data) \
--
2.53.0