[Bug 292515] Re: x86 ACPI: Fix breakage of resume on 64-bit UP systems with SMP kernel

[Mike Homer]

Here is some more info from 2.6.27.4 change log 
http://www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.27.4
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commit bc79810633524ea09b77e3de3ba3f4a97f2152b7
Author: Rafael J. Wysocki <rjw at sisk.pl>
Date:   Mon Oct 20 21:30:19 2008 +0000

    x86 ACPI: Fix breakage of resume on 64-bit UP systems with SMP kernel
    
    We are now using per CPU GDT tables in head_64.S and the original
    early_gdt_descr.address is invalidated after boot by
    setup_per_cpu_areas().  This breaks resume from suspend to RAM on
    x86_64 UP systems using SMP kernels, because this part of head_64.S
    is also executed during the resume and the invalid GDT address
    causes the system to crash.  It doesn't break on 'true' SMP systems,
    because early_gdt_descr.address is modified every time
    native_cpu_up() runs.  However, during resume it should point to the
    GDT of the boot CPU rather than to another CPU's GDT.
    
    For this reason, during suspend to RAM always make
    early_gdt_descr.address point to the boot CPU's GDT.

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x86 ACPI: Fix breakage of resume on 64-bit UP systems with SMP kernel
https://bugs.launchpad.net/bugs/292515
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