From 2896e068b6af7fcecb701f2b0da003bd762039cd Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 30 Jan 2008 13:30:02 +0100
Subject: [PATCH] --- yaml --- r: 79696 b: refs/heads/master c:
 316da3b3fc8efa9a5d2c99e0d449f01ff38c6aba h: refs/heads/master v: v3

---
 [refs]                        |  2 +-
 trunk/arch/x86/kernel/i8253.c | 10 +++++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/[refs] b/[refs]
index cf535d251148..7e58451de615 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: df619e6bafeb8e129aba3173d384544d7fa6e3c2
+refs/heads/master: 316da3b3fc8efa9a5d2c99e0d449f01ff38c6aba
diff --git a/trunk/arch/x86/kernel/i8253.c b/trunk/arch/x86/kernel/i8253.c
index a42c80745325..0f8f35458a8f 100644
--- a/trunk/arch/x86/kernel/i8253.c
+++ b/trunk/arch/x86/kernel/i8253.c
@@ -197,7 +197,15 @@ static struct clocksource clocksource_pit = {
 
 static int __init init_pit_clocksource(void)
 {
-	if (num_possible_cpus() > 1) /* PIT does not scale! */
+	 /*
+	  * Several reasons not to register PIT as a clocksource:
+	  *
+	  * - On SMP PIT does not scale due to i8253_lock
+	  * - when HPET is enabled
+	  * - when local APIC timer is active (PIT is switched off)
+	  */
+	if (num_possible_cpus() > 1 || is_hpet_enabled() ||
+	    pit_clockevent.mode != CLOCK_EVT_MODE_PERIODIC)
 		return 0;
 
 	clocksource_pit.mult = clocksource_hz2mult(CLOCK_TICK_RATE, 20);