[patch] SMP alternatives, take #2

From: Gerd Knorr (kraxel_at_suse.de)
Date: 11/30/05

  • Next message: Folkert van Heusden: "Re: [RFC] un petite hack: /proc/*/ctl" 
    Date:	Wed, 30 Nov 2005 11:19:24 +0100
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>

       Hi,

    Here next version of the SMP alternatives patch.

    Had a more detailed look at the bits generated, the vast majority in the
    smp alternatives table where simply lock prefixes. So I decided to
    specical-case these to keep the table sizes small. There are three elf
    sections now:

       .smp_altinstructions
       .smp_altinstr_replacement
           These are pretty much the same like the existing non-smp
           alternative bits, with the exception that the replacement
           table also has some space to keep the original instruction, to
           allow patching both SMP->UP and back UP->SMP. It's used to patch
           the code for spinlocks with simpler UP versions.

       .smp_locks
           List of pointers to the lock prefixes to be NOP'ed for UP.

    For the core kernel these three sections are grouped together and are
    page-aligned, so they can be freed. Freeing happens automatically in
    some cases where they not needed any more after booting up (UP system
    found, kernel without CONFIG_HOTPLUG_CPU). There is also a kernel cmd
    line option to force the tables being released.

    For modules only the .smp_locks section is handled, the other ones
    simply don't appear in modules ;)

    cheers,

       Gerd

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