http://bugzilla.kernel.org/show_bug.cgi?id=12468


[email protected] changed:

           What    |Removed                     |Added
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                 CC|                            |[email protected]




------- Comment #2 from [email protected]  2009-01-17 12:54 -------
And the first bad commit seem to be:

:HEAD ~/v2.6; git bisect good
50c668d678fd01284799a6e4f1b91829d83cb9ed is first bad commit
commit 50c668d678fd01284799a6e4f1b91829d83cb9ed
Author: Ingo Molnar <[email protected]>
Date:   Mon Jan 12 10:49:53 2009 +0100

    Revert "cpumask: use work_on_cpu in acpi-cpufreq.c for drv_read and
drv_writ
e"

    This reverts commit 7503bfbae89eba07b46441a5d1594647f6b8ab7d.

    Dieter Ries reported bootup soft-hangs and bisected it back to
    this commit, and reverting this commit gave him a working system.

    The commit introduces work_on_cpu() use into the cpufreq code,
    but that is subtly problematic from a lock hierarchy POV: the
    hotplug-cpu lock is an highlevel lock that is taken before
    lowlevel locks, and in this codepath we are called with the
    policy lock taken.

    Dieter did not have lockdep enabled so we dont have a nice stack
    trace proof for this, but using work_on_cpu() in such a lowlevel
    place certainly looks wrong, so we revert the patch.

    work_on_cpu() needs to be reworked to be more generally usable.

    Reported-by: Dieter Ries <[email protected]>
    Tested-by: Dieter Ries <[email protected]>
    Signed-off-by: Ingo Molnar <[email protected]>

M       arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c


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