http://bugzilla.kernel.org/show_bug.cgi?id=14700

           Summary: Broken system because of a bad ACPI commit
           Product: ACPI
           Version: 2.5
    Kernel Version: 2.6.31.9
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Power-Processor
        AssignedTo: acpi_power-proces...@kernel-bugs.osdl.org
        ReportedBy: pe...@digip.org
        Regression: Yes


After an upgrade to 2.6.31 kernel, the system is very unstable.
Sometimes it doesn't boot. If it does, the laptop keyboard doesn't
work and after a few minutes it hangs with ATA errors.

I bisected this problem down to the following commit:

commit ee1ca48fae7e575d5e399d4fdcfe0afc1212a64c
Author: Pallipadi, Venkatesh <venkatesh.pallip...@intel.com>
Date:   Thu May 21 17:09:10 2009 -0700

    ACPI: Disable ARB_DISABLE on platforms where it is not needed

    ARB_DISABLE is a NOP on all of the recent Intel platforms.

    For such platforms, reduce contention on c3_lock
    by skipping the fake ARB_DISABLE.

    Signed-off-by: Venkatesh Pallipadi <venkatesh.pallip...@intel.com>
    Signed-off-by: Len Brown <len.br...@intel.com>

With this commit reverted, the system works fine with 2.6.31.

$ cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 14
model name      : Intel(R) Celeron(R) M CPU        410  @ 1.46GHz
stepping        : 8
cpu MHz         : 1463.194
cache size      : 1024 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov
clflush dts acpi mmx fxsr sse sse2 ss tm pbe nx constant_tsc up arch_perfmon
bts pni monitor tm2 xtpr pdcm
bogomips        : 2926.38
clflush size    : 64
power management:

If I read the code correctly, in the commit message, "all of the
recent Intel platforms" seem to mean those with family == 6 and model
>= 14. My processor's model is 14 so could we have an
off-by-one error here?

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