tracing: likely/unlikely branch annotation tracer
Impact: new likely/unlikely branch tracer
This patch adds a way to record the instances of the likely() and unlikely()
branch condition annotations.
When "unlikely" is set in /debugfs/tracing/iter_ctrl the unlikely conditions
will be added to any of the ftrace tracers. The change takes effect when
a new tracer is passed into the current_tracer file.
For example:
bash-3471 [003] 357.014755: [INCORRECT] sched_info_dequeued:sched_stats.h:177
bash-3471 [003] 357.014756: [correct] update_curr:sched_fair.c:489
bash-3471 [003] 357.014758: [correct] calc_delta_fair:sched_fair.c:411
bash-3471 [003] 357.014759: [correct] account_group_exec_runtime:sched_stats.h:356
bash-3471 [003] 357.014761: [correct] update_curr:sched_fair.c:489
bash-3471 [003] 357.014763: [INCORRECT] calc_delta_fair:sched_fair.c:411
bash-3471 [003] 357.014765: [correct] calc_delta_mine:sched.c:1279
Which shows the normal tracer heading, as well as whether the condition was
correct "[correct]" or was mistaken "[INCORRECT]", followed by the function,
file name and line number.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index b5f91f1..9635aa2 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -22,6 +22,7 @@
TRACE_SPECIAL,
TRACE_MMIO_RW,
TRACE_MMIO_MAP,
+ TRACE_UNLIKELY,
TRACE_BOOT_CALL,
TRACE_BOOT_RET,
TRACE_FN_RET,
@@ -134,6 +135,16 @@
struct boot_trace_ret boot_ret;
};
+#define TRACE_FUNC_SIZE 30
+#define TRACE_FILE_SIZE 20
+struct trace_unlikely {
+ struct trace_entry ent;
+ unsigned line;
+ char func[TRACE_FUNC_SIZE+1];
+ char file[TRACE_FILE_SIZE+1];
+ char correct;
+};
+
/*
* trace_flag_type is an enumeration that holds different
* states when a trace occurs. These are:
@@ -236,6 +247,7 @@
TRACE_MMIO_MAP); \
IF_ASSIGN(var, ent, struct trace_boot_call, TRACE_BOOT_CALL);\
IF_ASSIGN(var, ent, struct trace_boot_ret, TRACE_BOOT_RET);\
+ IF_ASSIGN(var, ent, struct trace_unlikely, TRACE_UNLIKELY); \
IF_ASSIGN(var, ent, struct ftrace_ret_entry, TRACE_FN_RET);\
__ftrace_bad_type(); \
} while (0)
@@ -456,6 +468,9 @@
TRACE_ITER_SCHED_TREE = 0x200,
TRACE_ITER_PRINTK = 0x400,
TRACE_ITER_PREEMPTONLY = 0x800,
+#ifdef CONFIG_UNLIKELY_TRACER
+ TRACE_ITER_UNLIKELY = 0x1000,
+#endif
};
/*
@@ -515,4 +530,28 @@
preempt_enable_notrace();
}
+#ifdef CONFIG_UNLIKELY_TRACER
+extern int enable_unlikely_tracing(struct trace_array *tr);
+extern void disable_unlikely_tracing(void);
+static inline int trace_unlikely_enable(struct trace_array *tr)
+{
+ if (trace_flags & TRACE_ITER_UNLIKELY)
+ return enable_unlikely_tracing(tr);
+ return 0;
+}
+static inline void trace_unlikely_disable(void)
+{
+ /* due to races, always disable */
+ disable_unlikely_tracing();
+}
+#else
+static inline int trace_unlikely_enable(struct trace_array *tr)
+{
+ return 0;
+}
+static inline void trace_unlikely_disable(void)
+{
+}
+#endif /* CONFIG_UNLIKELY_TRACER */
+
#endif /* _LINUX_KERNEL_TRACE_H */