init, tracing: Add initcall trace events

Being able to trace the start and stop of initcalls is useful to see where
the timings are an issue. There is already an "initcall_debug" parameter,
but that can cause a large overhead itself, as the printing of the
information may take longer than the initcall functions.

Adding in a start and finish trace event around the initcall functions, as
well as a trace event that records the level of the initcalls, one can get a
much finer measurement of the times and interactions of the initcalls
themselves, as trace events are much lighter than printk()s.

Suggested-by: Abderrahmane Benbachir <abderrahmane.benbachir@polymtl.ca>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/init/main.c b/init/main.c
index 0ebdd5f15be8..2af8f2bb5ca8 100644
--- a/init/main.c
+++ b/init/main.c
@@ -97,6 +97,9 @@
 #include <asm/sections.h>
 #include <asm/cacheflush.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/initcall.h>
+
 static int kernel_init(void *);
 
 extern void init_IRQ(void);
@@ -827,10 +830,12 @@ int __init_or_module do_one_initcall(initcall_t fn)
 	if (initcall_blacklisted(fn))
 		return -EPERM;
 
+	trace_initcall_start(fn);
 	if (initcall_debug)
 		ret = do_one_initcall_debug(fn);
 	else
 		ret = fn();
+	trace_initcall_finish(fn, ret);
 
 	msgbuf[0] = 0;
 
@@ -895,6 +900,7 @@ static void __init do_initcall_level(int level)
 		   level, level,
 		   NULL, &repair_env_string);
 
+	trace_initcall_level(initcall_level_names[level]);
 	for (fn = initcall_levels[level]; fn < initcall_levels[level+1]; fn++)
 		do_one_initcall(*fn);
 }
@@ -929,6 +935,7 @@ static void __init do_pre_smp_initcalls(void)
 {
 	initcall_t *fn;
 
+	trace_initcall_level("early");
 	for (fn = __initcall_start; fn < __initcall0_start; fn++)
 		do_one_initcall(*fn);
 }