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![Tejun Heo](/assets/img/avatar_default.png)
Timer internals are protected with irq-safe locks but timer execution isn't, so a timer being dequeued for execution and its execution aren't atomic against IRQs. This makes it impossible to wait for its completion from IRQ handlers and difficult to shoot down a timer from IRQ handlers. This issue caused some issues for delayed_work interface. Because there's no way to reliably shoot down delayed_work->timer from IRQ handlers, __cancel_delayed_work() can't share the logic to steal the target delayed_work with cancel_delayed_work_sync(), and can only steal delayed_works which are on queued on timer. Similarly, the pending mod_delayed_work() can't be used from IRQ handlers. This patch adds a new timer flag TIMER_IRQSAFE, which makes the timer to be executed without enabling IRQ after dequeueing such that its dequeueing and execution are atomic against IRQ handlers. This makes it safe to wait for the timer's completion from IRQ handlers, for example, using del_timer_sync(). It can never be executing on the local CPU and if executing on other CPUs it won't be interrupted until done. This will enable simplifying delayed_work cancel/mod interface. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: torvalds@linux-foundation.org Cc: peterz@infradead.org Link: http://lkml.kernel.org/r/1344449428-24962-5-git-send-email-tj@kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
267 lines
7.9 KiB
C
267 lines
7.9 KiB
C
#ifndef _LINUX_TIMER_H
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#define _LINUX_TIMER_H
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#include <linux/list.h>
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#include <linux/ktime.h>
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#include <linux/stddef.h>
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#include <linux/debugobjects.h>
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#include <linux/stringify.h>
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struct tvec_base;
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struct timer_list {
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/*
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* All fields that change during normal runtime grouped to the
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* same cacheline
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*/
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struct list_head entry;
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unsigned long expires;
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struct tvec_base *base;
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void (*function)(unsigned long);
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unsigned long data;
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int slack;
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#ifdef CONFIG_TIMER_STATS
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int start_pid;
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void *start_site;
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char start_comm[16];
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#endif
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#ifdef CONFIG_LOCKDEP
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struct lockdep_map lockdep_map;
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#endif
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};
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extern struct tvec_base boot_tvec_bases;
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#ifdef CONFIG_LOCKDEP
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/*
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* NB: because we have to copy the lockdep_map, setting the lockdep_map key
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* (second argument) here is required, otherwise it could be initialised to
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* the copy of the lockdep_map later! We use the pointer to and the string
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* "<file>:<line>" as the key resp. the name of the lockdep_map.
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*/
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#define __TIMER_LOCKDEP_MAP_INITIALIZER(_kn) \
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.lockdep_map = STATIC_LOCKDEP_MAP_INIT(_kn, &_kn),
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#else
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#define __TIMER_LOCKDEP_MAP_INITIALIZER(_kn)
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#endif
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/*
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* Note that all tvec_bases are at least 4 byte aligned and lower two bits
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* of base in timer_list is guaranteed to be zero. Use them for flags.
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*
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* A deferrable timer will work normally when the system is busy, but
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* will not cause a CPU to come out of idle just to service it; instead,
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* the timer will be serviced when the CPU eventually wakes up with a
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* subsequent non-deferrable timer.
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*
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* An irqsafe timer is executed with IRQ disabled and it's safe to wait for
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* the completion of the running instance from IRQ handlers, for example,
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* by calling del_timer_sync().
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*
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* Note: The irq disabled callback execution is a special case for
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* workqueue locking issues. It's not meant for executing random crap
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* with interrupts disabled. Abuse is monitored!
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*/
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#define TIMER_DEFERRABLE 0x1LU
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#define TIMER_IRQSAFE 0x2LU
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#define TIMER_FLAG_MASK 0x3LU
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#define __TIMER_INITIALIZER(_function, _expires, _data, _flags) { \
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.entry = { .prev = TIMER_ENTRY_STATIC }, \
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.function = (_function), \
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.expires = (_expires), \
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.data = (_data), \
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.base = (void *)((unsigned long)&boot_tvec_bases + (_flags)), \
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.slack = -1, \
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__TIMER_LOCKDEP_MAP_INITIALIZER( \
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__FILE__ ":" __stringify(__LINE__)) \
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}
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#define TIMER_INITIALIZER(_function, _expires, _data) \
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__TIMER_INITIALIZER((_function), (_expires), (_data), 0)
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#define TIMER_DEFERRED_INITIALIZER(_function, _expires, _data) \
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__TIMER_INITIALIZER((_function), (_expires), (_data), TIMER_DEFERRABLE)
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#define DEFINE_TIMER(_name, _function, _expires, _data) \
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struct timer_list _name = \
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TIMER_INITIALIZER(_function, _expires, _data)
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void init_timer_key(struct timer_list *timer, unsigned int flags,
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const char *name, struct lock_class_key *key);
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#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
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extern void init_timer_on_stack_key(struct timer_list *timer,
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unsigned int flags, const char *name,
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struct lock_class_key *key);
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extern void destroy_timer_on_stack(struct timer_list *timer);
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#else
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static inline void destroy_timer_on_stack(struct timer_list *timer) { }
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static inline void init_timer_on_stack_key(struct timer_list *timer,
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unsigned int flags, const char *name,
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struct lock_class_key *key)
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{
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init_timer_key(timer, flags, name, key);
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}
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#endif
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#ifdef CONFIG_LOCKDEP
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#define __init_timer(_timer, _flags) \
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do { \
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static struct lock_class_key __key; \
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init_timer_key((_timer), (_flags), #_timer, &__key); \
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} while (0)
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#define __init_timer_on_stack(_timer, _flags) \
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do { \
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static struct lock_class_key __key; \
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init_timer_on_stack_key((_timer), (_flags), #_timer, &__key); \
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} while (0)
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#else
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#define __init_timer(_timer, _flags) \
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init_timer_key((_timer), (_flags), NULL, NULL)
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#define __init_timer_on_stack(_timer, _flags) \
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init_timer_on_stack_key((_timer), (_flags), NULL, NULL)
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#endif
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#define init_timer(timer) \
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__init_timer((timer), 0)
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#define init_timer_deferrable(timer) \
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__init_timer((timer), TIMER_DEFERRABLE)
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#define init_timer_on_stack(timer) \
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__init_timer_on_stack((timer), 0)
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#define __setup_timer(_timer, _fn, _data, _flags) \
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do { \
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__init_timer((_timer), (_flags)); \
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(_timer)->function = (_fn); \
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(_timer)->data = (_data); \
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} while (0)
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#define __setup_timer_on_stack(_timer, _fn, _data, _flags) \
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do { \
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__init_timer_on_stack((_timer), (_flags)); \
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(_timer)->function = (_fn); \
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(_timer)->data = (_data); \
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} while (0)
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#define setup_timer(timer, fn, data) \
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__setup_timer((timer), (fn), (data), 0)
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#define setup_timer_on_stack(timer, fn, data) \
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__setup_timer_on_stack((timer), (fn), (data), 0)
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#define setup_deferrable_timer_on_stack(timer, fn, data) \
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__setup_timer_on_stack((timer), (fn), (data), TIMER_DEFERRABLE)
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/**
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* timer_pending - is a timer pending?
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* @timer: the timer in question
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*
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* timer_pending will tell whether a given timer is currently pending,
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* or not. Callers must ensure serialization wrt. other operations done
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* to this timer, eg. interrupt contexts, or other CPUs on SMP.
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*
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* return value: 1 if the timer is pending, 0 if not.
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*/
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static inline int timer_pending(const struct timer_list * timer)
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{
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return timer->entry.next != NULL;
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}
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extern void add_timer_on(struct timer_list *timer, int cpu);
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extern int del_timer(struct timer_list * timer);
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extern int mod_timer(struct timer_list *timer, unsigned long expires);
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extern int mod_timer_pending(struct timer_list *timer, unsigned long expires);
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extern int mod_timer_pinned(struct timer_list *timer, unsigned long expires);
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extern void set_timer_slack(struct timer_list *time, int slack_hz);
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#define TIMER_NOT_PINNED 0
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#define TIMER_PINNED 1
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/*
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* The jiffies value which is added to now, when there is no timer
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* in the timer wheel:
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*/
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#define NEXT_TIMER_MAX_DELTA ((1UL << 30) - 1)
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/*
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* Return when the next timer-wheel timeout occurs (in absolute jiffies),
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* locks the timer base and does the comparison against the given
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* jiffie.
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*/
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extern unsigned long get_next_timer_interrupt(unsigned long now);
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/*
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* Timer-statistics info:
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*/
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#ifdef CONFIG_TIMER_STATS
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extern int timer_stats_active;
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#define TIMER_STATS_FLAG_DEFERRABLE 0x1
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extern void init_timer_stats(void);
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extern void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
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void *timerf, char *comm,
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unsigned int timer_flag);
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extern void __timer_stats_timer_set_start_info(struct timer_list *timer,
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void *addr);
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static inline void timer_stats_timer_set_start_info(struct timer_list *timer)
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{
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if (likely(!timer_stats_active))
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return;
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__timer_stats_timer_set_start_info(timer, __builtin_return_address(0));
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}
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static inline void timer_stats_timer_clear_start_info(struct timer_list *timer)
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{
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timer->start_site = NULL;
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}
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#else
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static inline void init_timer_stats(void)
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{
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}
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static inline void timer_stats_timer_set_start_info(struct timer_list *timer)
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{
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}
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static inline void timer_stats_timer_clear_start_info(struct timer_list *timer)
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{
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}
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#endif
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extern void add_timer(struct timer_list *timer);
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extern int try_to_del_timer_sync(struct timer_list *timer);
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#ifdef CONFIG_SMP
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extern int del_timer_sync(struct timer_list *timer);
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#else
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# define del_timer_sync(t) del_timer(t)
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#endif
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#define del_singleshot_timer_sync(t) del_timer_sync(t)
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extern void init_timers(void);
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extern void run_local_timers(void);
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struct hrtimer;
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extern enum hrtimer_restart it_real_fn(struct hrtimer *);
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unsigned long __round_jiffies(unsigned long j, int cpu);
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unsigned long __round_jiffies_relative(unsigned long j, int cpu);
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unsigned long round_jiffies(unsigned long j);
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unsigned long round_jiffies_relative(unsigned long j);
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unsigned long __round_jiffies_up(unsigned long j, int cpu);
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unsigned long __round_jiffies_up_relative(unsigned long j, int cpu);
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unsigned long round_jiffies_up(unsigned long j);
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unsigned long round_jiffies_up_relative(unsigned long j);
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#endif
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