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clockevents: Serialize calls to clockevents_update_freq() in the core
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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 <[email protected]>
Cc: [email protected]
Cc: Soeren Brinkmann <[email protected]>
Cc: Daniel Lezcano <[email protected]>
Cc: Michal Simek <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>
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KAGA-KOKO committed Feb 7, 2014
1 parent e8b1759 commit 627ee79
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Showing 3 changed files with 45 additions and 13 deletions.
29 changes: 22 additions & 7 deletions kernel/time/clockevents.c
Original file line number Diff line number Diff line change
Expand Up @@ -439,24 +439,39 @@ 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
* @freq: new device frequency
*
* 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;
}

/*
Expand Down
25 changes: 19 additions & 6 deletions kernel/time/tick-broadcast.c
Original file line number Diff line number Diff line change
Expand Up @@ -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");
Expand Down Expand Up @@ -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);
}

/*
Expand All @@ -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
Expand All @@ -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);
}

/*
Expand Down
4 changes: 4 additions & 0 deletions kernel/time/tick-internal.h
Original file line number Diff line number Diff line change
Expand Up @@ -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 */

Expand All @@ -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
Expand All @@ -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);

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