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SubjectRe: 2.6.16-rc1-mm4 i386 atomic operations broken on SMP (in modules at least)
Chuck Ebbert <76306.1226@compuserve.com> wrote:
>
> In-Reply-To: <17377.24090.486443.865483@cse.unsw.edu.au>
>
> On Thu, 2 Feb 2006 at 12:19:22 +1100, Neil Brown wrote:
>
> > My guess is there is there is something wrong with the 'alternative'
> > stuff which strips out the lock prefix, but I couldn't see anything
> > obviously wrong. The CPUs don't have FEATURE_UP (see below) so it
> > cannot possibly be removing the 'lock' prefix... but it certainly acts
> > like it is.
>
> Look closer:
>
> > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
> > cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe lm
> > constant_tsc pni monitor ds_cpl cid xtpr
> ^^^^^^^^^^^^
>
> SMP alternatives is re-using the constant_tsc X86 feature bit.
>
> --- 2.6.16-rc1-mm4-386.orig/include/asm-i386/cpufeature.h
> +++ 2.6.16-rc1-mm4-386/include/asm-i386/cpufeature.h
> @@ -71,7 +71,7 @@
> #define X86_FEATURE_P4 (3*32+ 7) /* P4 */
> #define X86_FEATURE_CONSTANT_TSC (3*32+ 8) /* TSC ticks at a constant rate */
>
> -#define X86_FEATURE_UP (3*32+ 8) /* smp kernel running on up */
> +#define X86_FEATURE_UP (3*32+ 9) /* smp kernel running on up */
>
> /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */
> #define X86_FEATURE_XMM3 (4*32+ 0) /* Streaming SIMD Extensions-3 */

Darn, how did you spot that?

Should `feature_up' appear in /proc/cpuinfo?
-
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