[PATCH] init/main.c: Use ktime accessor function in initcall_debug code.

[PATCH] init/main.c: Use ktime accessor function in initcall_debug code.

[Will Newton]

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The initcall_debug code access the tv64 member of ktime. This won't work
correctly for large deltas on platforms that don't use the scalar ktime
implementation.

Signed-off-by: Will Newton <will.newton@gmail.com>
---
 init/main.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/init/main.c b/init/main.c
index 7e117a2..0eff42a 100644
--- a/init/main.c
+++ b/init/main.c
@@ -718,7 +718,7 @@ int do_one_initcall(initcall_t fn)
 	if (initcall_debug) {
 		it.rettime = ktime_get();
 		delta = ktime_sub(it.rettime, it.calltime);
-		it.duration = (unsigned long long) delta.tv64 >> 10;
+		it.duration = (unsigned long long) ktime_to_ns(delta) >> 10;
 		printk("initcall %pF returned %d after %Ld usecs\n", fn,
 			it.result, it.duration);
 		trace_boot(&it, fn);
-- 
1.5.5.2

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From e9697ec9db4d04b9c615d34b76571afabaa8dfb1 Mon Sep 17 00:00:00 2001
From: Will Newton <will.newton@gmail.com>
Date: Thu, 20 Nov 2008 14:11:54 +0000
Subject: [PATCH] init/main.c: Use ktime accessor function in initcall_debug code.

The initcall_debug code access the tv64 member of ktime. This won't work
correctly on platforms that don't use the scalar ktime implementation.

Signed-off-by: Will Newton <will.newton@gmail.com>
---
 init/main.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/init/main.c b/init/main.c
index 7e117a2..0eff42a 100644
--- a/init/main.c
+++ b/init/main.c
@@ -718,7 +718,7 @@ int do_one_initcall(initcall_t fn)
 	if (initcall_debug) {
 		it.rettime = ktime_get();
 		delta = ktime_sub(it.rettime, it.calltime);
-		it.duration = (unsigned long long) delta.tv64 >> 10;
+		it.duration = (unsigned long long) ktime_to_ns(delta) >> 10;
 		printk("initcall %pF returned %d after %Ld usecs\n", fn,
 			it.result, it.duration);
 		trace_boot(&it, fn);
-- 
1.5.5.2

Re: [PATCH] init/main.c: Use ktime accessor function in initcall_debug code.

[Tim Bird]

Will Newton wrote:
> The initcall_debug code access the tv64 member of ktime. This won't work
> correctly for large deltas on platforms that don't use the scalar ktime
> implementation.

In principle I see no problem with this.  But as a matter of
practice it may be overkill.

How big does the delta have to be for this to be a problem?
And how much overhead does ktime_to_ns() add?
 -- Tim

=============================
Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Corporation of America
=============================

Re: [PATCH] init/main.c: Use ktime accessor function in initcall_debug code.

[Will Newton]

On Thu, Nov 20, 2008 at 5:39 PM, Tim Bird <tim.bird@am.sony.com> wrote:
> Will Newton wrote:
>> The initcall_debug code access the tv64 member of ktime. This won't work
>> correctly for large deltas on platforms that don't use the scalar ktime
>> implementation.
>
> In principle I see no problem with this.  But as a matter of
> practice it may be overkill.

Possibly, but it makes the code clearer I think.

> How big does the delta have to be for this to be a problem?
> And how much overhead does ktime_to_ns() add?

Deltas over a second will be incorrect. I have serial8250_init taking
8 seconds at the moment, so that isn't unheard of.

On scalar ktime architectures it should be zero, on others a multiply
and an add (it's an inline). I wouldn't call it a fast path though.

>  -- Tim
>
> =============================
> Tim Bird
> Architecture Group Chair, CE Linux Forum
> Senior Staff Engineer, Sony Corporation of America
> =============================
>
>

Re: [PATCH] init/main.c: Use ktime accessor function in initcall_debug code.

[Tim Bird]

Will Newton wrote:
> On Thu, Nov 20, 2008 at 5:39 PM, Tim Bird <tim.bird@am.sony.com> wrote:
>> Will Newton wrote:
>>> The initcall_debug code access the tv64 member of ktime. This won't work
>>> correctly for large deltas on platforms that don't use the scalar ktime
>>> implementation.
>> In principle I see no problem with this.  But as a matter of
>> practice it may be overkill.
> 
> Possibly, but it makes the code clearer I think.
> 
>> How big does the delta have to be for this to be a problem?
>> And how much overhead does ktime_to_ns() add?
> 
> Deltas over a second will be incorrect.

OK.  Good fix, then.

> I have serial8250_init taking
> 8 seconds at the moment, so that isn't unheard of.

This is likely the result of the emission of all
previously queued printks which occurs during serial8250_init()
(as a side effect of finally initializing the console).

I see this kind of long delay all the time.
If the 8 seconds is a bother, you might want
to use 'quiet' on the kernel command line.

I suspect you've already seen this page, but for future
readers of this thread, there's info on this at:
http://elinux.org/Disable_Console

> On scalar ktime architectures it should be zero, on others a multiply
> and an add (it's an inline). I wouldn't call it a fast path though.

OK.  You have my ACK.
 -- Tim

=============================
Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Corporation of America
=============================