From: Erik Jacobson <ejacobso@redhat.com>
Subject: [RHEL5 Patch] BZ 219722 Do not call SN_SAL_SET_CPU_NUMBER twice on cpu 0 on booting
Date: Thu, 14 Dec 2006 18:00:29 -0500
Bugzilla: 219722
Message-Id: <20061214230029.GA29300@redhat.com>
Changelog: ia64: Do not call SN_SAL_SET_CPU_NUMBER twice on cpu 0 on booting


Hi.  This is a RHEL5 kernel patch for bugzilla 219722.

Jay Lan has tested this patch with RHEL5 kernel-2.6.18-1.2767.el5.

The bug affects kexec/kdump support on ia64 Altix (SN).

This change is contained within SN-specific code.  So, as far as risk
goes, we'd only be hurting ourselves (sgi).

This patch has been discussed and accepted.

http://lists.osdl.org/pipermail/fastboot/2006-December/005315.html
http://marc.theaimsgroup.com/?l=linux-ia64&m=116597605326817&w=2

Index: linux/arch/ia64/sn/kernel/setup.c
===================================================================
--- linux.orig/arch/ia64/sn/kernel/setup.c	2006-12-11 13:16:14.000000000 -0800
+++ linux/arch/ia64/sn/kernel/setup.c	2006-12-11 13:28:01.084639511 -0800
@@ -574,7 +574,7 @@ void __cpuinit sn_cpu_init(void)
 	int slice;
 	int cnode;
 	int i;
-	static int wars_have_been_checked;
+	static int wars_have_been_checked, set_cpu0_number;
 
 	cpuid = smp_processor_id();
 	if (cpuid == 0 && IS_MEDUSA()) {
@@ -599,8 +599,16 @@ void __cpuinit sn_cpu_init(void)
 	/*
 	 * Don't check status. The SAL call is not supported on all PROMs
 	 * but a failure is harmless.
+	 * Architechtuallly, cpu_init is always called twice on cpu 0. We
+	 * should set cpu_number on cpu 0 once.
 	 */
-	(void) ia64_sn_set_cpu_number(cpuid);
+	if (cpuid == 0) {
+		if (!set_cpu0_number) {
+			(void) ia64_sn_set_cpu_number(cpuid);
+			set_cpu0_number = 1;
+		}
+	} else
+		(void) ia64_sn_set_cpu_number(cpuid);
 
 	/*
 	 * The boot cpu makes this call again after platform initialization is