2 files changed, 13 insertions, 35 deletions

diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 56d75afedbf7..aef494b6b81a 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -13,6 +13,7 @@
 #include "linux/ptrace.h"
 #include "linux/random.h"
 #include "linux/sched.h"
+#include "linux/tick.h"
 #include "linux/threads.h"
 #include "asm/pgtable.h"
 #include "asm/uaccess.h"
@@ -244,9 +245,11 @@ void default_idle(void)
                 if (need_resched())
                         schedule();
 
+                tick_nohz_stop_sched_tick();
                 switch_timers(1);
                 idle_sleep(10);
                 switch_timers(0);
+                tick_nohz_restart_sched_tick();
         }
 }
 
diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
index 3cb7135e5c47..2acdc7efb2ac 100644
--- a/arch/um/kernel/time.c
+++ b/arch/um/kernel/time.c
@@ -20,41 +20,12 @@ unsigned long long sched_clock(void)
         return (unsigned long long)jiffies_64 * (1000000000 / HZ);
 }
 
-#ifdef CONFIG_UML_REAL_TIME_CLOCK
-static unsigned long long prev_nsecs[NR_CPUS];
-static long long delta[NR_CPUS];                /* Deviation per interval */
-#endif
-
 void timer_handler(int sig, struct uml_pt_regs *regs)
 {
-        unsigned long long ticks = 0;
         unsigned long flags;
-#ifdef CONFIG_UML_REAL_TIME_CLOCK
-        int c = cpu();
-        if (prev_nsecs[c]) {
-                /* We've had 1 tick */
-                unsigned long long nsecs = os_nsecs();
-
-                delta[c] += nsecs - prev_nsecs[c];
-                prev_nsecs[c] = nsecs;
-
-                /* Protect against the host clock being set backwards */
-                if (delta[c] < 0)
-                        delta[c] = 0;
-
-                ticks += (delta[c] * HZ) / BILLION;
-                delta[c] -= (ticks * BILLION) / HZ;
-        }
-        else prev_nsecs[c] = os_nsecs();
-#else
-        ticks = 1;
-#endif
 
         local_irq_save(flags);
-        while (ticks > 0) {
-                do_IRQ(TIMER_IRQ, regs);
-                ticks--;
-        }
+        do_IRQ(TIMER_IRQ, regs);
         local_irq_restore(flags);
 }
 
@@ -68,10 +39,8 @@ static void itimer_set_mode(enum clock_event_mode mode,
 
         case CLOCK_EVT_MODE_SHUTDOWN:
         case CLOCK_EVT_MODE_UNUSED:
-                disable_timer();
-                break;
         case CLOCK_EVT_MODE_ONESHOT:
-                BUG();
+                disable_timer();
                 break;
 
         case CLOCK_EVT_MODE_RESUME:
@@ -79,13 +48,19 @@ static void itimer_set_mode(enum clock_event_mode mode,
         }
 }
 
+static int itimer_next_event(unsigned long delta,
+                             struct clock_event_device *evt)
+{
+        return timer_one_shot(delta + 1);
+}
+
 static struct clock_event_device itimer_clockevent = {
         .name           = "itimer",
         .rating         = 250,
         .cpumask        = CPU_MASK_ALL,
-        .features       = CLOCK_EVT_FEAT_PERIODIC,
+        .features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
         .set_mode       = itimer_set_mode,
-        .set_next_event = NULL,
+        .set_next_event = itimer_next_event,
         .shift          = 32,
         .irq            = 0,
 };