Re: [boot crash] Re: [tip:timers/core] clocksource: Resolve cpuhotplug dead lock with TSC unstable
From: john stultz
Date: Tue Sep 08 2009 - 17:43:24 EST
On Thu, 2009年09月03日 at 20:58 +0200, Ingo Molnar wrote:
>
* Ingo Molnar <mingo@xxxxxxx> wrote:
>
>
> i tried to bisect it but it's inconclusive:
>
>
>
> # bad: [32beef9c] Merge branch 'perfcounters/core'
>
> # bad: [b6413360] manual merge of x86/platform
>
> # bad: [d9e5f39a] Merge branch 'auto-oprofile-next' into auto-latest
>
> # bad: [cbaff272] Merge branch 'auto-timers-next' into auto-latest
>
>
>
> as the bisection comes up with that merge commit. Perhaps the
>
> combination of the x86/platform changes and the clocksource
>
> changes triggered it?
>
>
That seems to be the case - i just tested a combination merge of
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tip:auto-timers-next and tip:auto-x86-next and the result crashed in
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a similar way too.
>
>
Since normal bisection cannot find such breakages, i did a topical
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bisection (merging the finegrained tip:x86/* topics into the timer
>
tree gradually and testing each merge).
>
>
That way i could exclude: x86/platform, x86/pat, x86/asm, x86/apic,
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x86/percpu, x86/cpu, x86/mm and arrived to x86/tsc - which contains
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a single commit:
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>
d3b8f88: x86: Make tsc=reliable override boot time stability checks
>
>
Reverting that commit from tip:master gives me a non-crashing
>
bootup.
Huh. Does dropping the last chunk of the patch make the issue go away?
I'm suspecting fixing the bug Thomas noticed in the tsc_unstable
assignment (we set tsc_unstable before calling mark_tsc_unstable,
causing the TSC rating to not change) that I included in this patch is
colliding with the clocksource rework from Martin.
Although I'm not sure I see that in the backtrace, so I'm likely wrong.
Hrmm..
-john
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