enhance initcall_debug, measure latency

enhance the initcall_debug boot option:

 - measure the time the initcall took to execute and report
   it in units of milliseconds.

 - show the return code of initcalls (useful to see failures and
   to make sure that an initcall hung)

[akpm@linux-foundation.org: fix printk warning]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/init/main.c b/init/main.c
index 949c27b59d12..c1537e0ddceb 100644
--- a/init/main.c
+++ b/init/main.c
@@ -648,6 +648,7 @@ static void __init do_initcalls(void)
         int count = preempt_count();
 
         for (call = __initcall_start; call < __initcall_end; call++) {
+                ktime_t t0, t1, delta;
                 char *msg = NULL;
                 char msgbuf[40];
                 int result;
@@ -657,10 +658,26 @@ static void __init do_initcalls(void)
                         print_fn_descriptor_symbol(": %s()",
                                         (unsigned long) *call);
                         printk("\n");
+                        t0 = ktime_get();
                 }
 
                 result = (*call)();
 
+                if (initcall_debug) {
+                        t1 = ktime_get();
+                        delta = ktime_sub(t1, t0);
+
+                        printk("initcall 0x%p", *call);
+                        print_fn_descriptor_symbol(": %s()",
+                                        (unsigned long) *call);
+                        printk(" returned %d.\n", result);
+
+                        printk("initcall 0x%p ran for %Ld msecs: ",
+                                *call, (unsigned long long)delta.tv64 >> 20);
+                        print_fn_descriptor_symbol("%s()\n",
+                                (unsigned long) *call);
+                }
+
                 if (result && result != -ENODEV && initcall_debug) {
                         sprintf(msgbuf, "error code %d", result);
                         msg = msgbuf;