Re: [patch] SMP alternatives

[Gerd Knorr]

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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