Commit 2f0df49c authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware) Committed by Peter Zijlstra
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jump_label: Do not profile branch annotations 



While running my branch profiler that checks for incorrect "likely" and
"unlikely"s around the kernel, there's a large number of them that are
incorrect due to being "static_branches".

As static_branches are rather special, as they are likely or unlikely for
other reasons than normal annotations are used for, there's no reason to
have them be profiled.

Expose the "unlikely_notrace" and "likely_notrace" so that the
static_branch can use them, and have them be ignored by the branch
profilers.

Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201211163754.585174b9@gandalf.local.home
parent c7539258

include/linux/compiler.h

+2 −0
Original line number Diff line number Diff line
@@ -76,6 +76,8 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, 
#else

# define likely(x)	__builtin_expect(!!(x), 1)

# define unlikely(x)	__builtin_expect(!!(x), 0)

# define likely_notrace(x)	likely(x)

# define unlikely_notrace(x)	unlikely(x)

#endif



/* Optimization barrier */

include/linux/jump_label.h

+6 −6
Original line number Diff line number Diff line
@@ -261,14 +261,14 @@ static __always_inline void jump_label_init(void) 


static __always_inline bool static_key_false(struct static_key *key)

{

	if (unlikely(static_key_count(key) > 0))

	if (unlikely_notrace(static_key_count(key) > 0))

		return true;

	return false;

}



static __always_inline bool static_key_true(struct static_key *key)

{

	if (likely(static_key_count(key) > 0))

	if (likely_notrace(static_key_count(key) > 0))

		return true;

	return false;

}
@@ -460,7 +460,7 @@ extern bool ____wrong_branch_error(void); 
		branch = !arch_static_branch_jump(&(x)->key, true);		\

	else									\

		branch = ____wrong_branch_error();				\

	likely(branch);								\

	likely_notrace(branch);								\

})



#define static_branch_unlikely(x)						\
@@ -472,13 +472,13 @@ extern bool ____wrong_branch_error(void); 
		branch = arch_static_branch(&(x)->key, false);			\

	else									\

		branch = ____wrong_branch_error();				\

	unlikely(branch);							\

	unlikely_notrace(branch);							\

})



#else /* !CONFIG_JUMP_LABEL */



#define static_branch_likely(x)		likely(static_key_enabled(&(x)->key))

#define static_branch_unlikely(x)	unlikely(static_key_enabled(&(x)->key))

#define static_branch_likely(x)		likely_notrace(static_key_enabled(&(x)->key))

#define static_branch_unlikely(x)	unlikely_notrace(static_key_enabled(&(x)->key))



#endif /* CONFIG_JUMP_LABEL */