9 files changed, 66 insertions, 29 deletions

diff --git a/arch/arm/mach-at91/at91rm9200_time.c b/arch/arm/mach-at91/at91rm9200_time.c
index f607deb40f4d..bc7b363a3083 100644
--- a/arch/arm/mach-at91/at91rm9200_time.c
+++ b/arch/arm/mach-at91/at91rm9200_time.c
@@ -174,7 +174,6 @@ clkevt32k_next_event(unsigned long delta, struct clock_event_device *dev)
 static struct clock_event_device clkevt = {
         .name           = "at91_tick",
         .features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
-        .shift          = 32,
         .rating         = 150,
         .set_next_event = clkevt32k_next_event,
         .set_mode       = clkevt32k_mode,
@@ -265,11 +264,9 @@ void __init at91rm9200_timer_init(void)
         at91_st_write(AT91_ST_RTMR, 1);
 
         /* Setup timer clockevent, with minimum of two ticks (important!!) */
-        clkevt.mult = div_sc(AT91_SLOW_CLOCK, NSEC_PER_SEC, clkevt.shift);
-        clkevt.max_delta_ns = clockevent_delta2ns(AT91_ST_ALMV, &clkevt);
-        clkevt.min_delta_ns = clockevent_delta2ns(2, &clkevt) + 1;
         clkevt.cpumask = cpumask_of(0);
-        clockevents_register_device(&clkevt);
+        clockevents_config_and_register(&clkevt, AT91_SLOW_CLOCK,
+                                        2, AT91_ST_ALMV);
 
         /* register clocksource */
         clocksource_register_hz(&clk32k, AT91_SLOW_CLOCK);
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index bdb953e15d2a..5c07a56962db 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -87,6 +87,7 @@ config ARM_ARCH_TIMER
 config ARM_ARCH_TIMER_EVTSTREAM
         bool "Support for ARM architected timer event stream generation"
         default y if ARM_ARCH_TIMER
+        depends on ARM_ARCH_TIMER
         help
           This option enables support for event stream generation based on
           the ARM architected timer. It is used for waking up CPUs executing
diff --git a/drivers/clocksource/sh_mtu2.c b/drivers/clocksource/sh_mtu2.c
index 4aac9ee0d0c0..3cf12834681e 100644
--- a/drivers/clocksource/sh_mtu2.c
+++ b/drivers/clocksource/sh_mtu2.c
@@ -313,8 +313,20 @@ static int sh_mtu2_setup(struct sh_mtu2_priv *p, struct platform_device *pdev)
                 goto err1;
         }
 
-        return sh_mtu2_register(p, (char *)dev_name(&p->pdev->dev),
-                                cfg->clockevent_rating);
+        ret = clk_prepare(p->clk);
+        if (ret < 0)
+                goto err2;
+
+        ret = sh_mtu2_register(p, (char *)dev_name(&p->pdev->dev),
+                               cfg->clockevent_rating);
+        if (ret < 0)
+                goto err3;
+
+        return 0;
+ err3:
+        clk_unprepare(p->clk);
+ err2:
+        clk_put(p->clk);
  err1:
         iounmap(p->mapbase);
  err0:
diff --git a/drivers/clocksource/sh_tmu.c b/drivers/clocksource/sh_tmu.c
index 78b8dae49628..63557cda0a7d 100644
--- a/drivers/clocksource/sh_tmu.c
+++ b/drivers/clocksource/sh_tmu.c
@@ -472,12 +472,26 @@ static int sh_tmu_setup(struct sh_tmu_priv *p, struct platform_device *pdev)
                 ret = PTR_ERR(p->clk);
                 goto err1;
         }
+
+        ret = clk_prepare(p->clk);
+        if (ret < 0)
+                goto err2;
+
         p->cs_enabled = false;
         p->enable_count = 0;
 
-        return sh_tmu_register(p, (char *)dev_name(&p->pdev->dev),
-                               cfg->clockevent_rating,
-                               cfg->clocksource_rating);
+        ret = sh_tmu_register(p, (char *)dev_name(&p->pdev->dev),
+                              cfg->clockevent_rating,
+                              cfg->clocksource_rating);
+        if (ret < 0)
+                goto err3;
+
+        return 0;
+
+ err3:
+        clk_unprepare(p->clk);
+ err2:
+        clk_put(p->clk);
  err1:
         iounmap(p->mapbase);
  err0:
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 6abb03dff5c0..08a765232432 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1632,7 +1632,7 @@ module_param(rcu_idle_gp_delay, int, 0644);
 static int rcu_idle_lazy_gp_delay = RCU_IDLE_LAZY_GP_DELAY;
 module_param(rcu_idle_lazy_gp_delay, int, 0644);
 
-extern int tick_nohz_enabled;
+extern int tick_nohz_active;
 
 /*
  * Try to advance callbacks for all flavors of RCU on the current CPU, but
@@ -1729,7 +1729,7 @@ static void rcu_prepare_for_idle(int cpu)
         int tne;
 
         /* Handle nohz enablement switches conservatively. */
-        tne = ACCESS_ONCE(tick_nohz_enabled);
+        tne = ACCESS_ONCE(tick_nohz_active);
         if (tne != rdtp->tick_nohz_enabled_snap) {
                 if (rcu_cpu_has_callbacks(cpu, NULL))
                         invoke_rcu_core(); /* force nohz to see update. */
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 64522ecdfe0e..162b03ab0ad2 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -33,6 +33,21 @@ DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
  */
 ktime_t tick_next_period;
 ktime_t tick_period;
+
+/*
+ * tick_do_timer_cpu is a timer core internal variable which holds the CPU NR
+ * which is responsible for calling do_timer(), i.e. the timekeeping stuff. This
+ * variable has two functions:
+ *
+ * 1) Prevent a thundering herd issue of a gazillion of CPUs trying to grab the
+ *    timekeeping lock all at once. Only the CPU which is assigned to do the
+ *    update is handling it.
+ *
+ * 2) Hand off the duty in the NOHZ idle case by setting the value to
+ *    TICK_DO_TIMER_NONE, i.e. a non existing CPU. So the next cpu which looks
+ *    at it will take over and keep the time keeping alive.  The handover
+ *    procedure also covers cpu hotplug.
+ */
 int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
 
 /*
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 3612fc77f834..ea20f7d1ac2c 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -361,8 +361,8 @@ void __init tick_nohz_init(void)
 /*
  * NO HZ enabled ?
  */
-int tick_nohz_enabled __read_mostly  = 1;
-
+static int tick_nohz_enabled __read_mostly  = 1;
+int tick_nohz_active  __read_mostly;
 /*
  * Enable / Disable tickless mode
  */
@@ -465,7 +465,7 @@ u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
         struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
         ktime_t now, idle;
 
-        if (!tick_nohz_enabled)
+        if (!tick_nohz_active)
                 return -1;
 
         now = ktime_get();
@@ -506,7 +506,7 @@ u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
         struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
         ktime_t now, iowait;
 
-        if (!tick_nohz_enabled)
+        if (!tick_nohz_active)
                 return -1;
 
         now = ktime_get();
@@ -711,8 +711,10 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
                 return false;
         }
 
-        if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
+        if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) {
+                ts->sleep_length = (ktime_t) { .tv64 = NSEC_PER_SEC/HZ };
                 return false;
+        }
 
         if (need_resched())
                 return false;
@@ -799,11 +801,6 @@ void tick_nohz_idle_enter(void)
         local_irq_disable();
 
         ts = &__get_cpu_var(tick_cpu_sched);
-        /*
-         * set ts->inidle unconditionally. even if the system did not
-         * switch to nohz mode the cpu frequency governers rely on the
-         * update of the idle time accounting in tick_nohz_start_idle().
-         */
         ts->inidle = 1;
         __tick_nohz_idle_enter(ts);
 
@@ -973,7 +970,7 @@ static void tick_nohz_switch_to_nohz(void)
         struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
         ktime_t next;
 
-        if (!tick_nohz_enabled)
+        if (!tick_nohz_active)
                 return;
 
         local_irq_disable();
@@ -981,7 +978,7 @@ static void tick_nohz_switch_to_nohz(void)
                 local_irq_enable();
                 return;
         }
-
+        tick_nohz_active = 1;
         ts->nohz_mode = NOHZ_MODE_LOWRES;
 
         /*
@@ -1139,8 +1136,10 @@ void tick_setup_sched_timer(void)
         }
 
 #ifdef CONFIG_NO_HZ_COMMON
-        if (tick_nohz_enabled)
+        if (tick_nohz_enabled) {
                 ts->nohz_mode = NOHZ_MODE_HIGHRES;
+                tick_nohz_active = 1;
+        }
 #endif
 }
 #endif /* HIGH_RES_TIMERS */
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 3abf53418b67..87b4f00284c9 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1347,7 +1347,7 @@ static inline void old_vsyscall_fixup(struct timekeeper *tk)
         tk->xtime_nsec -= remainder;
         tk->xtime_nsec += 1ULL << tk->shift;
         tk->ntp_error += remainder << tk->ntp_error_shift;
-
+        tk->ntp_error -= (1ULL << tk->shift) << tk->ntp_error_shift;
 }
 #else
 #define old_vsyscall_fixup(tk)
diff --git a/kernel/timer.c b/kernel/timer.c
index 6582b82fa966..accfd241b9e5 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1518,9 +1518,8 @@ static int init_timers_cpu(int cpu)
                         /*
                          * The APs use this path later in boot
                          */
-                        base = kmalloc_node(sizeof(*base),
-                                                GFP_KERNEL | __GFP_ZERO,
-                                                cpu_to_node(cpu));
+                        base = kzalloc_node(sizeof(*base), GFP_KERNEL,
+                                            cpu_to_node(cpu));
                         if (!base)
                                 return -ENOMEM;