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) \
--
2.53.0On Thu, 12 Mar 2026 11:04:56 -0400
"Vineeth Pillai (Google)" <vineeth@bitbyteword.org> wrote:
> 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
I'm guessing Claude helped with the other patches. Did it really help with this one?
-- Steve
> ---
> 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) \
On Thu, Mar 12, 2026 at 11:13 AM Steven Rostedt <rostedt@goodmis.org> wrote: > > On Thu, 12 Mar 2026 11:04:56 -0400 > "Vineeth Pillai (Google)" <vineeth@bitbyteword.org> wrote: > > > 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 > > I'm guessing Claude helped with the other patches. Did it really help with this one? > Claude wrote and build tested the whole series based on my guidance and prompt :-). I verified the series before sending it out, but claude did the initial work. Thanks, Vineeth
On Thu, Mar 12, 2026 at 11:39:06AM -0400, Vineeth Remanan Pillai wrote: > On Thu, Mar 12, 2026 at 11:13 AM Steven Rostedt <rostedt@goodmis.org> wrote: > > > > On Thu, 12 Mar 2026 11:04:56 -0400 > > "Vineeth Pillai (Google)" <vineeth@bitbyteword.org> wrote: > > > > > 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 > > > > I'm guessing Claude helped with the other patches. Did it really help with this one? > > > > Claude wrote and build tested the whole series based on my guidance > and prompt :-). I verified the series before sending it out, but > claude did the initial work. That seems like an unreasonable waste of energy. You could've had claude write a Coccinelle script for you and saved a ton of tokens.
On Thu, Mar 12, 2026 at 11:53 AM Peter Zijlstra <peterz@infradead.org> wrote: > > On Thu, Mar 12, 2026 at 11:39:06AM -0400, Vineeth Remanan Pillai wrote: > > On Thu, Mar 12, 2026 at 11:13 AM Steven Rostedt <rostedt@goodmis.org> wrote: > > > > > > On Thu, 12 Mar 2026 11:04:56 -0400 > > > "Vineeth Pillai (Google)" <vineeth@bitbyteword.org> wrote: > > > > > > > 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 > > > > > > I'm guessing Claude helped with the other patches. Did it really help with this one? > > > > > > > Claude wrote and build tested the whole series based on my guidance > > and prompt :-). I verified the series before sending it out, but > > claude did the initial work. > > That seems like an unreasonable waste of energy. You could've had claude > write a Coccinelle script for you and saved a ton of tokens. Yeah true, Steve also mentioned this to me offline. Haven't used Coccinelle before, but now I know :-) Thanks, Vineeth
On Thu, Mar 12, 2026 at 12:05:37PM -0400, Vineeth Remanan Pillai wrote: > On Thu, Mar 12, 2026 at 11:53 AM Peter Zijlstra <peterz@infradead.org> wrote: > > > > That seems like an unreasonable waste of energy. You could've had claude > > write a Coccinelle script for you and saved a ton of tokens. > > Yeah true, Steve also mentioned this to me offline. Haven't used > Coccinelle before, but now I know :-) [+ Chris Mason] At the risk of creating a distraction... This discussion got me thinking the right skill loaded should have the AI implicitly use coccinelle to generate the patchset rather than do it by hand. You could prompt with simple language for a pattern substitution rather than explicitly request coccinelle, and it should generate a patch set using a script rather than spending tokens on doing it "by hand". I sent such a "skill" to Chris' kernel "review-prompts": https://github.com/masoncl/review-prompts/pull/35 I used patch one from this series as the starting point and let the AI figure the rest out. The result actually found additional patterns that could take advantage of the optimisation that this series did not include. The resulting kernel tree that the above github pull request references cost 2.8k tokens to create with the skill.
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