fb02fbc14d
We did not restart the tick device from irq_enter() to avoid double
reprogramming and extra events in the return immediate to idle case.
But long lasting softirqs can lead to a situation where jiffies become
stale:
idle()
tick stopped (reprogrammed to next pending timer)
halt()
interrupt
jiffies updated from irq_enter()
interrupt handler
softirq function 1 runs 20ms
softirq function 2 arms a 10ms timer with a stale jiffies value
jiffies updated from irq_exit()
timer wheel has now an already expired timer
(the one added in function 2)
timer fires and timer softirq runs
This was discovered when debugging a timer problem which happend only
when the ath5k driver is active. The debugging proved that there is a
softirq function running for more than 20ms, which is a bug by itself.
To solve this we restart the tick timer right from irq_enter(), but do
not go through the other functions which are necessary to return from
idle when need_resched() is set.
Reported-by: Elias Oltmanns <eo@nebensachen.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Elias Oltmanns <eo@nebensachen.de>
135 lines
4.4 KiB
C
135 lines
4.4 KiB
C
/*
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* tick internal variable and functions used by low/high res code
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*/
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#define TICK_DO_TIMER_NONE -1
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#define TICK_DO_TIMER_BOOT -2
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DECLARE_PER_CPU(struct tick_device, tick_cpu_device);
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extern spinlock_t tick_device_lock;
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extern ktime_t tick_next_period;
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extern ktime_t tick_period;
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extern int tick_do_timer_cpu __read_mostly;
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extern void tick_setup_periodic(struct clock_event_device *dev, int broadcast);
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extern void tick_handle_periodic(struct clock_event_device *dev);
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extern void clockevents_shutdown(struct clock_event_device *dev);
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/*
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* NO_HZ / high resolution timer shared code
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*/
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#ifdef CONFIG_TICK_ONESHOT
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extern void tick_setup_oneshot(struct clock_event_device *newdev,
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void (*handler)(struct clock_event_device *),
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ktime_t nextevt);
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extern int tick_dev_program_event(struct clock_event_device *dev,
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ktime_t expires, int force);
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extern int tick_program_event(ktime_t expires, int force);
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extern void tick_oneshot_notify(void);
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extern int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *));
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extern void tick_resume_oneshot(void);
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# ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
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extern void tick_broadcast_setup_oneshot(struct clock_event_device *bc);
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extern void tick_broadcast_oneshot_control(unsigned long reason);
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extern void tick_broadcast_switch_to_oneshot(void);
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extern void tick_shutdown_broadcast_oneshot(unsigned int *cpup);
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extern int tick_resume_broadcast_oneshot(struct clock_event_device *bc);
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extern int tick_broadcast_oneshot_active(void);
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extern void tick_check_oneshot_broadcast(int cpu);
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# else /* BROADCAST */
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static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
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{
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BUG();
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}
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static inline void tick_broadcast_oneshot_control(unsigned long reason) { }
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static inline void tick_broadcast_switch_to_oneshot(void) { }
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static inline void tick_shutdown_broadcast_oneshot(unsigned int *cpup) { }
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static inline int tick_broadcast_oneshot_active(void) { return 0; }
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static inline void tick_check_oneshot_broadcast(int cpu) { }
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# endif /* !BROADCAST */
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#else /* !ONESHOT */
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static inline
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void tick_setup_oneshot(struct clock_event_device *newdev,
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void (*handler)(struct clock_event_device *),
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ktime_t nextevt)
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{
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BUG();
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}
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static inline void tick_resume_oneshot(void)
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{
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BUG();
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}
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static inline int tick_program_event(ktime_t expires, int force)
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{
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return 0;
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}
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static inline void tick_oneshot_notify(void) { }
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static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
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{
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BUG();
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}
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static inline void tick_broadcast_oneshot_control(unsigned long reason) { }
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static inline void tick_shutdown_broadcast_oneshot(unsigned int *cpup) { }
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static inline int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
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{
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return 0;
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}
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static inline int tick_broadcast_oneshot_active(void) { return 0; }
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#endif /* !TICK_ONESHOT */
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/*
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* Broadcasting support
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*/
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#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
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extern int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu);
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extern int tick_check_broadcast_device(struct clock_event_device *dev);
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extern int tick_is_broadcast_device(struct clock_event_device *dev);
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extern void tick_broadcast_on_off(unsigned long reason, int *oncpu);
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extern void tick_shutdown_broadcast(unsigned int *cpup);
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extern void tick_suspend_broadcast(void);
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extern int tick_resume_broadcast(void);
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extern void
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tick_set_periodic_handler(struct clock_event_device *dev, int broadcast);
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#else /* !BROADCAST */
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static inline int tick_check_broadcast_device(struct clock_event_device *dev)
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{
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return 0;
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}
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static inline int tick_is_broadcast_device(struct clock_event_device *dev)
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{
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return 0;
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}
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static inline int tick_device_uses_broadcast(struct clock_event_device *dev,
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int cpu)
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{
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return 0;
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}
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static inline void tick_do_periodic_broadcast(struct clock_event_device *d) { }
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static inline void tick_broadcast_on_off(unsigned long reason, int *oncpu) { }
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static inline void tick_shutdown_broadcast(unsigned int *cpup) { }
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static inline void tick_suspend_broadcast(void) { }
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static inline int tick_resume_broadcast(void) { return 0; }
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/*
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* Set the periodic handler in non broadcast mode
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*/
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static inline void tick_set_periodic_handler(struct clock_event_device *dev,
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int broadcast)
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{
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dev->event_handler = tick_handle_periodic;
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}
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#endif /* !BROADCAST */
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/*
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* Check, if the device is functional or a dummy for broadcast
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*/
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static inline int tick_device_is_functional(struct clock_event_device *dev)
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{
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return !(dev->features & CLOCK_EVT_FEAT_DUMMY);
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}
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