From: Vineeth Pillai (Google) <vineeth@bitbyteword.org>
Date: Mon, 23 Mar 2026 16:00:20 +0000 (-0400)
Subject: tracepoint: Add trace_call__##name() API
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=677a3d82b6407522d922705209c311e043a17813;p=thirdparty%2Fkernel%2Flinux.git

tracepoint: Add trace_call__##name() API

Add trace_call__##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_call__##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.

Cc: Dmitry Ilvokhin <d@ilvokhin.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Cc: Xin Long <lucien.xin@gmail.com>
Cc: Jon Maloy <jmaloy@redhat.com>
Cc: Aaron Conole <aconole@redhat.com>
Cc: Eelco Chaudron <echaudro@redhat.com>
Cc: Ilya Maximets <i.maximets@ovn.org>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: Oded Gabbay <ogabbay@kernel.org>
Cc: Koby Elbaz <koby.elbaz@intel.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: "Gautham R. Shenoy" <gautham.shenoy@amd.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Chanwoo Choi <cw00.choi@samsung.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Eddie James <eajames@linux.ibm.com>
Cc: Andrew Jeffery <andrew@codeconstruct.com.au>
Cc: Joel Stanley <joel@jms.id.au>
Cc: David Airlie <airlied@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Philipp Stanner <phasta@kernel.org>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Benjamin Tissoires <bentiss@kernel.org>
Cc: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michael Hennerich <michael.hennerich@analog.com>
Cc: Nuno Sá <nuno.sa@analog.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Chris Mason <clm@fb.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20260323160052.17528-2-vineeth@bitbyteword.org
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Vineeth Pillai (Google) <vineeth@bitbyteword.org>
Assisted-by: Claude:claude-sonnet-4-6
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 22ca1c8b54f32..ed969705341f1 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_call__##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_call__##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_call__##name(proto)			\
+	{ }								\
 	static inline int						\
 	register_trace_##name(void (*probe)(data_proto),		\
 			      void *data)				\