2 files changed, 27 insertions, 8 deletions

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 18b9f5da4ee9..592bf584d1d2 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -30,7 +30,6 @@
 #include <linux/module.h>
 #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
 #include <linux/tick.h>
-#include <linux/hrtimer.h>
 
 void timecounter_init(struct timecounter *tc,
                       const struct cyclecounter *cc,
@@ -511,13 +510,13 @@ static ssize_t sysfs_override_clocksource(struct sys_device *dev,
         }
 
         /*
-         * Check to make sure we don't switch to a non-HRT usable
-         * clocksource if HRT is enabled and running
+         * 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 (hrtimer_hres_active() &&
+        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 mode\n", ovr->name);
+                        "Cannot switch while in HRT/NOHZ mode\n", ovr->name);
                 ovr = NULL;
                 override_name[0] = 0;
         }
@@ -550,9 +549,12 @@ sysfs_show_available_clocksources(struct sys_device *dev,
 
         spin_lock_irq(&clocksource_lock);
         list_for_each_entry(src, &clocksource_list, list) {
-                /* Don't show non-HRES clocksource if HRES is enabled */
-                if (!hrtimer_hres_active() ||
-                                (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
+                /*
+                 * 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);
diff --git a/kernel/time/tick-oneshot.c b/kernel/time/tick-oneshot.c
index 2e8de678e767..a96c0e2b89cf 100644
--- a/kernel/time/tick-oneshot.c
+++ b/kernel/time/tick-oneshot.c
@@ -128,6 +128,23 @@ int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
         return 0;
 }
 
+/**
+ * tick_check_oneshot_mode - check whether the system is in oneshot mode
+ *
+ * returns 1 when either nohz or highres are enabled. otherwise 0.
+ */
+int tick_oneshot_mode_active(void)
+{
+        unsigned long flags;
+        int ret;
+
+        local_irq_save(flags);
+        ret = __get_cpu_var(tick_cpu_device).mode == TICKDEV_MODE_ONESHOT;
+        local_irq_restore(flags);
+
+        return ret;
+}
+
 #ifdef CONFIG_HIGH_RES_TIMERS
 /**
  * tick_init_highres - switch to high resolution mode