Re: 2.6.16-rc1-mm4 i386 atomic operations broken on SMP (in modules at least)

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In-Reply-To: <[email protected]>

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 */
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