1 files changed, 19 insertions, 4 deletions

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index ecfd7b5187e0..592bf584d1d2 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -402,9 +402,6 @@ int clocksource_register(struct clocksource *c)
         unsigned long flags;
         int ret;
 
-        /* save mult_orig on registration */
-        c->mult_orig = c->mult;
-
         spin_lock_irqsave(&clocksource_lock, flags);
         ret = clocksource_enqueue(c);
         if (!ret)
@@ -512,6 +509,18 @@ static ssize_t sysfs_override_clocksource(struct sys_device *dev,
                 }
         }
 
+        /*
+         * Check to make sure we don't switch to a non-highres capable
+         * clocksource if the tick code is in oneshot mode (highres or nohz)
+         */
+        if (tick_oneshot_mode_active() &&
+            !(ovr->flags & CLOCK_SOURCE_VALID_FOR_HRES)) {
+                printk(KERN_WARNING "%s clocksource is not HRT compatible. "
+                        "Cannot switch while in HRT/NOHZ mode\n", ovr->name);
+                ovr = NULL;
+                override_name[0] = 0;
+        }
+
         /* Reselect, when the override name has changed */
         if (ovr != clocksource_override) {
                 clocksource_override = ovr;
@@ -540,7 +549,13 @@ sysfs_show_available_clocksources(struct sys_device *dev,
 
         spin_lock_irq(&clocksource_lock);
         list_for_each_entry(src, &clocksource_list, list) {
-                count += snprintf(buf + count,
+                /*
+                 * Don't show non-HRES clocksource if the tick code is
+                 * in one shot mode (highres=on or nohz=on)
+                 */
+                if (!tick_oneshot_mode_active() ||
+                    (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
+                        count += snprintf(buf + count,
                                   max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
                                   "%s ", src->name);
         }