Hi, everyoneI am implementing a simple driver to experiment with wait queue.Two or more read processes block until a write process changes a flag and call wake_up_interruptible().I expect that a write process will only wake up one read process.However, once a write process calls wake_up_interruptible() , all the read processes are awaken. How can I wake up one process from the wait queue? Here is the snippet of the simple dirver(just for experimenting, kernel 2.6.18): static ssize_t rlwait_read(struct file *filp, char __user *userp, size_t size, loff_t *off){ struct rlwait_t *rock = (struct rlwait_t *)filp->private_data; DECLARE_WAITQUEUE(wait, current); add_wait_queue(&rock->r_wait_head, &wait); while (rock->r_flag == 0) { set_current_state(TASK_INTERRUPTIBLE); schedule(); } remove_wait_queue(&rock->r_wait_head, &wait); set_current_state(TASK_RUNNING); return 0;} static ssize_t rlwait_write(struct file *filp, const char __user *userp, size_t size, loff_t *off){ struct rlwait_t *rock = (struct rlwait_t *)filp->private_data; rock->r_flag = 1; wake_up_interruptible(&rock->r_wait_head); return size; } Thans in advice.