clockevents: Serialize calls to clockevents_update_freq() in the core

We can identify the broadcast device in the core and serialize all
callers including interrupts on a different CPU against the update.
Also, disabling interrupts is moved into the core allowing callers to
leave interrutps enabled when calling clockevents_update_freq().

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Soeren Brinkmann <soren.brinkmann@xilinx.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Michal Simek <michal.simek@xilinx.com>
Link: http://lkml.kernel.org/r/1391466877-28908-2-git-send-email-soren.brinkmann@xilinx.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 45 insertions, 13 deletions

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 086ad6043bcb..641d91003a45 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -439,6 +439,16 @@ void clockevents_config_and_register(struct clock_event_device *dev,
 }
 EXPORT_SYMBOL_GPL(clockevents_config_and_register);
 
+int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
+{
+        clockevents_config(dev, freq);
+
+        if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
+                return 0;
+
+        return clockevents_program_event(dev, dev->next_event, false);
+}
+
 /**
  * clockevents_update_freq - Update frequency and reprogram a clock event device.
  * @dev:        device to modify
@@ -446,17 +456,22 @@ EXPORT_SYMBOL_GPL(clockevents_config_and_register);
  *
  * Reconfigure and reprogram a clock event device in oneshot
  * mode. Must be called on the cpu for which the device delivers per
- * cpu timer events with interrupts disabled!  Returns 0 on success,
- * -ETIME when the event is in the past.
+ * cpu timer events. If called for the broadcast device the core takes
+ * care of serialization.
+ *
+ * Returns 0 on success, -ETIME when the event is in the past.
  */
 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
 {
-        clockevents_config(dev, freq);
-
-        if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
-                return 0;
+        unsigned long flags;
+        int ret;
 
-        return clockevents_program_event(dev, dev->next_event, false);
+        local_irq_save(flags);
+        ret = tick_broadcast_update_freq(dev, freq);
+        if (ret == -ENODEV)
+                ret = __clockevents_update_freq(dev, freq);
+        local_irq_restore(flags);
+        return ret;
 }
 
 /*
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 43780ab5e279..003e6c3663b1 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -120,6 +120,19 @@ int tick_is_broadcast_device(struct clock_event_device *dev)
         return (dev && tick_broadcast_device.evtdev == dev);
 }
 
+int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
+{
+        int ret = -ENODEV;
+
+        if (tick_is_broadcast_device(dev)) {
+                raw_spin_lock(&tick_broadcast_lock);
+                ret = __clockevents_update_freq(dev, freq);
+                raw_spin_unlock(&tick_broadcast_lock);
+        }
+        return ret;
+}
+
+
 static void err_broadcast(const struct cpumask *mask)
 {
         pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
@@ -272,12 +285,8 @@ static void tick_do_broadcast(struct cpumask *mask)
  */
 static void tick_do_periodic_broadcast(void)
 {
-        raw_spin_lock(&tick_broadcast_lock);
-
         cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
         tick_do_broadcast(tmpmask);
-
-        raw_spin_unlock(&tick_broadcast_lock);
 }
 
 /*
@@ -287,13 +296,15 @@ static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 {
         ktime_t next;
 
+        raw_spin_lock(&tick_broadcast_lock);
+
         tick_do_periodic_broadcast();
 
         /*
          * The device is in periodic mode. No reprogramming necessary:
          */
         if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
-                return;
+                goto unlock;
 
         /*
          * Setup the next period for devices, which do not have
@@ -306,9 +317,11 @@ static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
                 next = ktime_add(next, tick_period);
 
                 if (!clockevents_program_event(dev, next, false))
-                        return;
+                        goto unlock;
                 tick_do_periodic_broadcast();
         }
+unlock:
+        raw_spin_unlock(&tick_broadcast_lock);
 }
 
 /*
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 8329669b51ec..26f1c0ba9d81 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -111,6 +111,7 @@ extern int tick_resume_broadcast(void);
 extern void tick_broadcast_init(void);
 extern void
 tick_set_periodic_handler(struct clock_event_device *dev, int broadcast);
+int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq);
 
 #else /* !BROADCAST */
 
@@ -133,6 +134,8 @@ static inline void tick_shutdown_broadcast(unsigned int *cpup) { }
 static inline void tick_suspend_broadcast(void) { }
 static inline int tick_resume_broadcast(void) { return 0; }
 static inline void tick_broadcast_init(void) { }
+static inline int tick_broadcast_update_freq(struct clock_event_device *dev,
+                                             u32 freq) { return -ENODEV; }
 
 /*
  * Set the periodic handler in non broadcast mode
@@ -154,5 +157,6 @@ static inline int tick_device_is_functional(struct clock_event_device *dev)
 
 #endif
 
+int __clockevents_update_freq(struct clock_event_device *dev, u32 freq);
 extern void do_timer(unsigned long ticks);
 extern void update_wall_time(void);