From 8bf53b0095abd294bafd286928cb4a2eaa5cceec Mon Sep 17 00:00:00 2001
From: Christoph Lameter <clameter@sgi.com>
Date: Wed, 1 Aug 2007 13:49:45 -0700
Subject: [PATCH] --- yaml --- r: 63562 b: refs/heads/master c:
 b718f91c14604e4ab5cdfe8d3baff8111425ea7d h: refs/heads/master v: v3

---
 [refs]                        |  2 +-
 trunk/arch/ia64/kernel/time.c | 16 +++++++++++++++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/[refs] b/[refs]
index 186af246225b..ffd3fd155a07 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 40d485753423b87239cc16b6c8141ef8792324d9
+refs/heads/master: b718f91c14604e4ab5cdfe8d3baff8111425ea7d
diff --git a/trunk/arch/ia64/kernel/time.c b/trunk/arch/ia64/kernel/time.c
index 6c0e9e2e1b82..98cfc90cab1d 100644
--- a/trunk/arch/ia64/kernel/time.c
+++ b/trunk/arch/ia64/kernel/time.c
@@ -240,7 +240,21 @@ ia64_init_itm (void)
 		if (!nojitter)
 			itc_jitter_data.itc_jitter = 1;
 #endif
-	}
+	} else
+		/*
+		 * ITC is drifty and we have not synchronized the ITCs in smpboot.c.
+		 * ITC values may fluctuate significantly between processors.
+		 * Clock should not be used for hrtimers. Mark itc as only
+		 * useful for boot and testing.
+		 *
+		 * Note that jitter compensation is off! There is no point of
+		 * synchronizing ITCs since they may be large differentials
+		 * that change over time.
+		 *
+		 * The only way to fix this would be to repeatedly sync the
+		 * ITCs. Until that time we have to avoid ITC.
+		 */
+		clocksource_itc.rating = 50;
 
 	/* Setup the CPU local timer tick */
 	ia64_cpu_local_tick();