tracing/fastboot: Enable boot tracing only during initcalls
Impact: modify boot tracer
We used to disable the initcall tracing at a specified time (IE: end
of builtin initcalls). But we don't need it anymore. It will be
stopped when initcalls are finished.
However we want two things:
_Start this tracing only after pre-smp initcalls are finished.
_Since we are planning to trace sched_switches at the same time, we
want to enable them only during the initcall execution.
For this purpose, this patch introduce two functions to enable/disable
the sched_switch tracing during boot.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index e46a7b3..4642959 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -234,6 +234,11 @@
#endif
+/*
+ * Structure which defines the trace of an initcall.
+ * You don't have to fill the func field since it is
+ * only used internally by the tracer.
+ */
struct boot_trace {
pid_t caller;
char func[KSYM_NAME_LEN];
@@ -244,13 +249,28 @@
};
#ifdef CONFIG_BOOT_TRACER
+/* Append the trace on the ring-buffer */
extern void trace_boot(struct boot_trace *it, initcall_t fn);
+
+/* Tells the tracer that smp_pre_initcall is finished.
+ * So we can start the tracing
+ */
extern void start_boot_trace(void);
-extern void stop_boot_trace(void);
+
+/* Resume the tracing of other necessary events
+ * such as sched switches
+ */
+extern void enable_boot_trace(void);
+
+/* Suspend this tracing. Actually, only sched_switches tracing have
+ * to be suspended. Initcalls doesn't need it.)
+ */
+extern void disable_boot_trace(void);
#else
static inline void trace_boot(struct boot_trace *it, initcall_t fn) { }
static inline void start_boot_trace(void) { }
-static inline void stop_boot_trace(void) { }
+static inline void enable_boot_trace(void) { }
+static inline void disable_boot_trace(void) { }
#endif