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    SubjectRe: CPU hyperthreading turned on after soft power-cycle
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    On Fri, 2011-11-18 at 00:42 +0100, Jiri Polach wrote:
    > On 11/17/2011 9:32 PM, John Stultz wrote:
    > > On Wed, 2011-11-16 at 23:49 +0100, Clarinet wrote:
    > >> Hi all,
    > >>
    > >>>> Result of bisecting: v2.6.38-rc1 exhibits the problem. v2.6.37 and
    > >>>> many of the topic branches merged in the 2.6.38 merge window work ok.
    > >>>> Some other topic branches do not boot at all.
    > >>>>
    > >>>> Jiri: if you have gitk installed, then "git bisect visualize" can help
    > >>>> get a sense of what's in the middle of the regression range.
    > >>>> "gitk --bisect --first-parent v2.6.37..v2.6.38-rc1" might be a good way
    > >>>> to find mainline commits to test before finding a topic branch to delve
    > >>>> into.
    > >>>
    > >>> I have been able to narrow the interval manually a little bit from the
    > >>> "top" (the bad side) and I will go on from the bottom now. However,
    > >>> there seems to be a large area where kernels are unbootable for me -
    > >>> they mostly stop when init is called and I do not know why.
    > >>
    > >> Finally! After another 50+ compilations a have it! It took some time as
    > >> first I had to find a reason why some revisions did not boot (almost 2/3
    > >> were unbootable and the first bad commit was among them). Having this
    > >> solved I have been able to bisect without "skipping". The result is
    > >> surprising (at least for me) - believe it or not, the first bad commit
    > >> is 6610e089 "RTC: Rework RTC code to use timerqueue for events" from
    > >> John Stultz (I am sending him a copy of this message).
    > >>
    > >> I would never expect this would be a problem, but my understanding of
    > >> this commit is very limited, so I am certainly missing the point.
    > >> However, I have tried to compile 2.6.38 (which was "bad") with "Real
    > >> Time Clock" configuration option turned off and it behaves "normally"
    > >> then (= is "good").
    > >
    > > Huh. That's *very* odd. Is your system doing anything in-particular
    > > with the RTC? I don't have a clue right off, so probably the next step
    >
    > Yes, it is very odd. The system does not do anything special with RTC.
    > It is a diskless computational workstation.
    >
    > > is doing a bit of instrumentation to try to figure out where exactly we
    > > trigger the behavior. Could you checkout commit 6610e089 and apply the
    > > patch below to see if we can't narrow it down?
    >
    > With the patch applied the system does not show the strange behavior (=
    > is "good").
    >
    > > Could you also send your .config to me?
    >
    > Sure. It is attached. I have found that if I turn CONFIG_RTC_DRV_CMOS
    > off, the system behaves normally (= is "good") too.

    Yea. My rough guess is that the BIOS is somehow sensitive to how the
    CMOS RTC is touched.

    Does disabling CONFIG_HPET_EMULATE_RTC change the behavior?

    thanks
    -john






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