From 38296ea0eb4d6210c6567532692d1b8ff91ed1d9 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Wed, 10 Mar 1999 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1999-03-10

---
 pc/clock.c |  2 ++
 pc/mp.c    | 10 ++++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/pc/clock.c b/pc/clock.c
index a036d7efd41ee324490a55f963cca8e2a0347869..7d14d6487b6689e495ff47bfa9134d8a8be957e1 100644
--- a/pc/clock.c
+++ b/pc/clock.c
@@ -38,6 +38,8 @@ clockintr(Ureg* ureg, void*)
 {
 	Clock0link *lp;
 
+	// this needs to be here for synchronizing mp clocks
+	// see mp.c's squidboy()
 	fastticks(nil);
 	m->ticks++;
 	if(m->proc)
diff --git a/pc/mp.c b/pc/mp.c
index c7fafbe14c057ea94edb3caa27a1da5a90c70e97..2196a80e925c6b676bfddceb8466d7070846e945 100644
--- a/pc/mp.c
+++ b/pc/mp.c
@@ -351,6 +351,8 @@ checkmtrr(void)
 static void
 squidboy(Apic* apic)
 {
+	ulong x;
+
 //	iprint("Hello Squidboy\n");
 
 	machinit();
@@ -367,8 +369,12 @@ squidboy(Apic* apic)
 	/*
 	 * Restrain your octopus! Don't let it go out on the sea!
 	 */
-	while(MACHP(0)->ticks == 0)
-		wrmsr(0x10, MACHP(0)->fastclock); /* synchronize fast counters */
+	lock(&active);
+	x = MACHP(0)->ticks;
+	while(MACHP(0)->ticks == x)
+		;
+	wrmsr(0x10, MACHP(0)->fastclock); /* synchronize fast counters */
+	unlock(&active);
 
 	lapicinit(apic);
 	lapiconline();