Re: [PATCH 1/2] time: Serialize calls to 'clockevents_update_freq'in the timing core
From: Daniel Lezcano
Date: Wed Dec 11 2013 - 09:33:07 EST
On 12/10/2013 01:34 AM, Soren Brinkmann wrote:
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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().
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Soren Brinkmann <soren.brinkmann@xxxxxxxxxx>
---
kernel/time/clockevents.c | 29 ++++++++++++++++++++++-------
kernel/time/tick-broadcast.c | 25 +++++++++++++++++++------
kernel/time/tick-internal.h | 4 ++++
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);
+}
+
./arch/arm/kernel/smp_twd.c should be modified to call
__clockevents_update_freq instead of clockevents_update_freq, no ?
/**
* 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 9532690daaa9..63a33b33fc4e 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 18e71f7fbc2a..22fd431a02eb 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
@@ -154,4 +157,5 @@ 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);
--
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