1 files changed, 15 insertions, 1 deletions

diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index 6c0e9e2e1b82..98cfc90cab1d 100644
--- a/arch/ia64/kernel/time.c
+++ b/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();