Re: [RFC][PATCH] fix target_cpus() for summit subarch

[john stultz]

On Mon, 2004-08-30 at 14:24, James Cleverdon wrote:
> I'm fine with changing the delivery mode to dest_LowestPrio.  However, 
> someone changed the default destination mask that target_cpus() returns 
> from XAPIC_DEST_CPUS_MASK (0F) to APIC_ALL_CPUS (FF).  The latter value 
> is a bad idea.  I'm unaware of anyone's hardware that will correctly 
> arbitrate dest_LowestPrio among all CPUs of all clusters.  (Please 
> correct me if I'm wrong.)  By chance, FF mostly works on IBM Summit 
> (EXA) chips, but we can't rely on that in the future.

Ok, here is the corrected patch. Ran it through LTP for awhile and
tested a few hotplug USB devices. 

If there are no other comments, I'll submit this to Andrew later this
week.

thanks


linux-2.6.9-rc1_summit-target-cpus-fix_A1
-----------------------------------------
diff -Nru a/include/asm-i386/mach-summit/mach_apic.h b/include/asm-i386/mach-summit/mach_apic.h
--- a/include/asm-i386/mach-summit/mach_apic.h	2004-08-30 17:33:02 -07:00
+++ b/include/asm-i386/mach-summit/mach_apic.h	2004-08-30 17:33:02 -07:00
@@ -19,11 +19,15 @@
 
 static inline cpumask_t target_cpus(void)
 {
-	return CPU_MASK_ALL;
+	/* CPU_MASK_ALL (0xff) has undefined behaviour with
+	 * logical clustered apic interrupt routing.
+	 * Just start on cpu 0.  IRQ balancing will spread load 
+	 */
+	return cpumask_of_cpu(0);
 } 
 #define TARGET_CPUS	(target_cpus())
 
-#define INT_DELIVERY_MODE (dest_Fixed)
+#define INT_DELIVERY_MODE (dest_LowestPrio)
 #define INT_DEST_MODE 1     /* logical delivery broadcast to all procs */
 
 static inline unsigned long check_apicid_used(physid_mask_t bitmap, int apicid)


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