睡眠_等待_阻塞_唤醒

睡眠， 等待， 阻塞，应该是一个概念

睡眠相关的代码位于

/include/linux/wait.h  和 /kernel/wait.c 中

 

1. 进入睡眠：

    /**
     * wait_event - sleep until a condition gets true
     * @wq: the waitqueue to wait on
     * @condition: a C expression for the event to wait for
     *
     * The process is put to sleep (TASK_UNINTERRUPTIBLE) until the
     * @condition evaluates to true. The @condition is checked each time
     * the waitqueue @wq is woken up.
     *
     * wake_up() has to be called after changing any variable that could
     * change the result of the wait condition.
     */
    #define wait_event(wq, condition)                     \
    do {                                    \
        if (condition)                             \
            break;                            \
        __wait_event(wq, condition);                    \
    } while (0)

    #define __wait_event(wq, condition)                     \
    do {                                    \
        DEFINE_WAIT(__wait);                        \
                                        \
        for (;;) {                            \
            prepare_to_wait(&wq, &__wait, TASK_UNINTERRUPTIBLE);    \
            if (condition)                        \
                break;                        \
            schedule();                        \
        }                                \
        finish_wait(&wq, &__wait);                    \
    } while (0)

条件判断 condition 用来实现这个睡眠、唤醒机制，

等待就是进入睡眠，需要 满足条件condition 来唤醒。

2. 唤醒

    #define wake_up(x)            __wake_up(x, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE, 1, NULL)
    #define wake_up_nr(x, nr)        __wake_up(x, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE, nr, NULL)
    #define wake_up_all(x)            __wake_up(x, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE, 0, NULL)
    #define wake_up_interruptible(x)    __wake_up(x, TASK_INTERRUPTIBLE, 1, NULL)
    #define wake_up_interruptible_nr(x, nr)    __wake_up(x, TASK_INTERRUPTIBLE, nr, NULL)
    #define wake_up_interruptible_all(x)    __wake_up(x, TASK_INTERRUPTIBLE, 0, NULL)
    #define    wake_up_locked(x)        __wake_up_locked((x), TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE)
    #define wake_up_interruptible_sync(x) __wake_up_sync((x),TASK_INTERRUPTIBLE, 1)

各种唤醒函数.

    /**
     * __wake_up - wake up threads blocked on a waitqueue.
     * @q: the waitqueue
     * @mode: which threads
     * @nr_exclusive: how many wake-one or wake-many threads to wake up
     * @key: is directly passed to the wakeup function
     */
    void fastcall __wake_up(wait_queue_head_t *q, unsigned int mode,
                int nr_exclusive, void *key)
    {
        unsigned long flags;
        spin_lock_irqsave(&q->lock, flags);
        __wake_up_common(q, mode, nr_exclusive, 0, key);
        spin_unlock_irqrestore(&q->lock, flags);
    }
    EXPORT_SYMBOL(__wake_up);