Date: Thu, 5 Nov 2009 16:33:21 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>, Valdis.Kletnieks@vt.edu,
       Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       Ingo Molnar <mingo@elte.hu>, Heiko Carstens <heiko.carstens@de.ibm.com>,
       Martin Schwidefsky <schwidefsky@googlemail.com>
Subject: Re: 2.6.32-rc5-mmotm1101 - lockdep whinge during early boot
Message-ID: <20091105153321.GB24690@redhat.com>
References: <6417.1257351084@turing-police.cc.vt.edu> <200911051941.03401.rusty@rustcorp.com.au> <20091105141055.GA17350@redhat.com> <alpine.LFD.2.00.0911051547110.12138@localhost.localdomain> <20091105152241.GA24690@redhat.com>
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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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