[patch] SMP alternatives, take #2

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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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• text/x-patch attachment: smp-alternatives-31.diff

• Previous message: Pierre Ossman: "Re: [Fwd: [PATCH] [PNP][RFC] Suspend support for PNP bus.]"
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