10
當使用add_timer
API創建的定時器過期並且在定時器結構中分配的功能運行時,它在什麼情況下運行?它是中斷上下文還是內核進程上下文?Linux內核定時器函數在哪個上下文中運行?
當使用add_timer
API創建的定時器過期並且在定時器結構中分配的功能運行時,它在什麼情況下運行?它是中斷上下文還是內核進程上下文?Linux內核定時器函數在哪個上下文中運行?
當然,在中斷上下文,更確切地說,在軟中斷上下文,見下文(核心/ timer.c中):
static inline void __run_timers(struct tvec_base *base)
{
struct timer_list *timer;
spin_lock_irq(&base->lock);
while (time_after_eq(jiffies, base->timer_jiffies)) {
struct list_head work_list;
struct list_head *head = &work_list;
int index = base->timer_jiffies & TVR_MASK;
/*
* Cascade timers:
*/
if (!index &&
(!cascade(base, &base->tv2, INDEX(0))) &&
(!cascade(base, &base->tv3, INDEX(1))) &&
!cascade(base, &base->tv4, INDEX(2)))
cascade(base, &base->tv5, INDEX(3));
++base->timer_jiffies;
list_replace_init(base->tv1.vec + index, &work_list);
while (!list_empty(head)) {
void (*fn)(unsigned long);
unsigned long data;
bool irqsafe;
timer = list_first_entry(head, struct timer_list,entry);
fn = timer->function;
data = timer->data;
irqsafe = tbase_get_irqsafe(timer->base);
timer_stats_account_timer(timer);
base->running_timer = timer;
detach_expired_timer(timer, base);
if (irqsafe) {
spin_unlock(&base->lock);
call_timer_fn(timer, fn, data); // <=========== HERE
spin_lock(&base->lock);
} else {
spin_unlock_irq(&base->lock);
call_timer_fn(timer, fn, data); // <============ HERE
spin_lock_irq(&base->lock);
}
}
}
base->running_timer = NULL;
spin_unlock_irq(&base->lock);
}
/*
* This function runs timers and the timer-tq in bottom half context.
*/
static void run_timer_softirq(struct softirq_action *h)
{
struct tvec_base *base = __this_cpu_read(tvec_bases);
hrtimer_run_pending();
if (time_after_eq(jiffies, base->timer_jiffies))
__run_timers(base);
}
void __init init_timers(void)
{
int err;
/* ensure there are enough low bits for flags in timer->base pointer */
BUILD_BUG_ON(__alignof__(struct tvec_base) & TIMER_FLAG_MASK);
err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
(void *)(long)smp_processor_id());
init_timer_stats();
BUG_ON(err != NOTIFY_OK);
register_cpu_notifier(&timers_nb);
open_softirq(TIMER_SOFTIRQ, run_timer_softirq); // <============= HERE
}
你說的是什麼操作系統?如果你的意思是Linux及其內核定時器,那麼它就是中斷上下文,因爲'linux/timer.c'中add_timer()的註釋表明:「內核將執行一個 - >函數( - > data)回調**從定時器中斷**到未來的 - >過期點。「雖然中斷處理程序可能在某些內核的進程上下文中運行,但我不建議依靠它。 – Eugene
嗨,對不起,當然Linux內核。謝謝。 – user1977760