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Date: Fri, 10 Oct 2008 16:47:46 +0200
From: "=?ISO-8859-1?Q?Fr=E9d=E9ric_Weisbecker?=" <fweisbec@gmail.com>
To: "Ingo Molnar" <mingo@elte.hu>
Subject: Re: [PATCH 6/6] tracing/fastboot: Print ktime of sched events when boot tracing
Cc: "Arjan van de Ven" <arjan@infradead.org>,
       "Steven Rostedt" <rostedt@goodmis.org>,
       Linux-Kernel <linux-kernel@vger.kernel.org>
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2008/10/10 Ingo Molnar <mingo@elte.hu>:
>
> * Frederic Weisbecker <fweisbec@gmail.com> wrote:
>
>> When we use the boot tracer, we want the sched events to be printed
>> with the same timestamp than initcall events. So we have to create a
>> new type of entry which contains sched event attributes and the ktime
>> of the creation of the entry. Then the output is handled by the boot
>> tracer.
>
> hm, i think that's unnecessary duplication. Please extend the context
> switch trace entries to be useful for the boot tracer as well:
>

Ok. I will change it in V2.

> also, ktime_get() can be a quite complex function with dependency on
> xtime_lock - that inverts with the rq lock - so this can lock up
> sporadically when called from within the scheduler.
> it would be _much_ simpler to standardize the initcall timestamps on
> cpu_clock() instead. That too is a good global clock and starts at zero
> during bootup. Ok?

Hmm. Ok, I will pick what I saw about cpu_clock() in printk.c

> Your other patches look good and i've applied them to
> tip/tracing/fastboot:
>
>  3981ce9: tracing/fastboot: use sched switch tracer from boot tracer
>  563582a: tracing/ftrace: remove unused code in sched_switch tracer
>  d25b1ce: tracing/ftrace: fix a race condition in sched_switch tracer

Thanks. But are you really sure about d25b1ce?
Steven suggested some changes. But it doesn't matter, I can apply his
suggestions on top of this applied patch.