Re: [patch] SMP alternatives

From: Gerd Knorr
Date: Wed Nov 23 2005 - 11:43:13 EST


Alan Cox wrote:
On Mer, 2005-11-23 at 12:17 -0700, Andi Kleen wrote:
+ /* Paranoia */
+ asm volatile ("jmp 1f\n1:");
+ mb();
That would be totally obsolete 386 era paranoia. If anything then use a CLFLUSH (but not available on all x86s)

If you are patching code another x86 CPU is running you must halt the
other processors and ensure it executes a serialzing instruction before
it enters any patched code.

Patching in/out SMP-locking with more than one active CPU would be a pretty silly idea in the first place ;)

How many kilobytes of tables do you add to the kernel to do this
pointless stunt btw ?

16 .smp_altinstructions 0000ae0b c03b4000 003b4000 002b4000 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
17 .smp_altinstr_replacement 00000f6e c03bee0b 003bee0b 002bee0b 2**0
CONTENTS, ALLOC, LOAD, CODE

cheers,

Gerd

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