From d940687d9bf0f6071270110efe4dacb3b31a677d Mon Sep 17 00:00:00 2001
From: macallan <macallan@NetBSD.org>
Date: Fri, 6 Aug 2010 00:07:05 +0000
Subject: [PATCH] do a better job synchronizing %tick across CPUs ok'ed by mrg

---
 sys/arch/sparc64/sparc64/cpu.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/sys/arch/sparc64/sparc64/cpu.c b/sys/arch/sparc64/sparc64/cpu.c
index 9ce3b493fde3..ea861e56a2b1 100644
--- a/sys/arch/sparc64/sparc64/cpu.c
+++ b/sys/arch/sparc64/sparc64/cpu.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: cpu.c,v 1.96 2010/07/28 21:34:57 macallan Exp $ */
+/*	$NetBSD: cpu.c,v 1.97 2010/08/06 00:07:05 macallan Exp $ */
 
 /*
  * Copyright (c) 1996
@@ -52,7 +52,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: cpu.c,v 1.96 2010/07/28 21:34:57 macallan Exp $");
+__KERNEL_RCSID(0, "$NetBSD: cpu.c,v 1.97 2010/08/06 00:07:05 macallan Exp $");
 
 #include "opt_multiprocessor.h"
 
@@ -106,6 +106,8 @@ static const char *ipi_evcnt_names[IPI_EVCNT_NUM] = IPI_EVCNT_NAMES;
 
 static void cpu_reset_fpustate(void);
 
+volatile int sync_tick = 0;
+
 /* The CPU configuration driver. */
 void cpu_attach(struct device *, struct device *, void *);
 int cpu_match(struct device *, struct cfdata *, void *);
@@ -412,6 +414,8 @@ cpu_boot_secondary_processors(void)
 	int i, pstate;
 	struct cpu_info *ci;
 
+	sync_tick = 0;
+
 	sparc64_ipi_init();
 
 	if (boothowto & RB_MD1) {
@@ -441,7 +445,13 @@ cpu_boot_secondary_processors(void)
 				break;
 			delay(10000);
 		}
+
+		/* synchronize %tick ( to some degree at least ) */
+		delay(1000);
+		sync_tick = 1;
+		membar_sync();
 		settick(0);
+
 		setpstate(pstate);
 
 		if (!CPUSET_HAS(cpus_active, ci->ci_index))
@@ -463,7 +473,13 @@ cpu_hatch(void)
 	cpu_reset_fpustate();
 	curlwp = curcpu()->ci_data.cpu_idlelwp;
 	membar_sync();
+
+	/* wait for the boot CPU to flip the switch */
+	while (sync_tick == 0) {
+		/* we do nothing here */
+	}
 	settick(0);
+
 	tickintr_establish(PIL_CLOCK, tickintr);
 	spl0();
 }