linux-kernel - Re: 2.6.32-rc5-mmotm1101 - lockdep whinge during early boot

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Date:	Thu, 5 Nov 2009 16:33:21 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Rusty Russell <rusty@...tcorp.com.au>, Valdis.Kletnieks@...edu,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...glemail.com>
Subject: Re: 2.6.32-rc5-mmotm1101 - lockdep whinge during early boot

On 11/05, Oleg Nesterov wrote:
>
> On 11/05, Thomas Gleixner wrote:
> >
> > Hmm, we fixed all this lock madness in mainline already.
> > clocksource_done_booting() does not longer call
> > create_workqueue(). How got this code reverted in motm ?
>
> I don't understand this code at all. But this is what I see
> in Linus's tree:
>
> 	clocksource_done_booting
> 	    clocksource_select
> 	        timekeeping_notify
> 	            stop_machine
> 	                 stop_machine_create
>
>
> OTOH, I don't see where native_cpu_up() path calls clocksource_change_rating(),
> perhaps this was changed in -mm.

I believe Martin knows the answer:

On 11/05, Martin Schwidefsky wrote:
>
> That is imho caused by this patch snippet from the linux-next.patch from mmotd:
>
> diff -puN arch/x86/kernel/tsc.c~linux-next arch/x86/kernel/tsc.c
> --- a/arch/x86/kernel/tsc.c~linux-next
> +++ a/arch/x86/kernel/tsc.c
> @@ -763,14 +763,12 @@ void mark_tsc_unstable(char *reason)
>  {
>         if (!tsc_unstable) {
>                 tsc_unstable = 1;
> -               printk(KERN_INFO "Marking TSC unstable due to %s\n", reason);
> +               printk("Marking TSC unstable due to %s\n", reason);
>                 /* Change only the rating, when not registered */
>                 if (clocksource_tsc.mult)
> -                       clocksource_mark_unstable(&clocksource_tsc);
> -               else {
> -                       clocksource_tsc.flags |= CLOCK_SOURCE_UNSTABLE;
> +                       clocksource_change_rating(&clocksource_tsc, 0);

                          ^^^^^^^^^^^^^^^^^^^^^^^^^

Oleg.

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