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6441402b1f
Impact: rare hang which can be triggered on CPU online.
tick_do_timer_cpu keeps track of the CPU which updates jiffies
via do_timer. The value -1 is used to signal, that currently no
CPU is doing this. There are two cases, where the variable can
have this state:
boot:
necessary for systems where the boot cpu id can be != 0
nohz long idle sleep:
When the CPU which did the jiffies update last goes into
a long idle sleep it drops the update jiffies duty so
another CPU which is not idle can pick it up and keep
jiffies going.
Using the same value for both situations is wrong, as the CPU online
code can see the -1 state when the timer of the newly onlined CPU is
setup. The setup for a newly onlined CPU goes through periodic mode
and can pick up the do_timer duty without being aware of the nohz /
highres mode of the already running system.
Use two separate states and make them constants to avoid magic
numbers confusion.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
131 lines
4.1 KiB
C
131 lines
4.1 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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# 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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# 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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#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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