[PATCH] jump_label: Do not profile branch annotations

From: Steven Rostedt
Date: Fri Dec 11 2020 - 16:39:34 EST


From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>

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: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index e512f5505dad..bbd141cf4b46 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -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 */
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index 32809624d422..d92691262f51 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -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 */