各驱动和内核机制中直接调用

SYSCALL_DEFINE1(exit, int, error_code) //exit.c 将 (error_code&0xff)<<8 传给参数 code

    do_exit(code);

        if (unlikely(in_interrupt())) //当前进程关中断后退出了，panic。

            panic("Aiee, killing interrupt handler!");

        if (unlikely(!tsk->pid)) //当前进程关抢占后退出了，panic。

            panic("Attempted to kill the idle task!");

        exit_signals(tsk);

            tsk->flags |= PF_EXITING; //标记进程正在退出

        if (unlikely(is_global_init(tsk))) //init进程退出了，panic。

            panic("Attempted to kill init! exitcode=0x%08x\n", tsk->signal->group_exit_code ?: (int)code);

        tsk->exit_code = code; //更新退出码

        exit_notify(tsk, group_dead);

            tsk->exit_state = EXIT_ZOMBIE;

        exit_rcu(); //通知RCU进程退出了

        do_task_dead

            tsk->state |= TASK_DEAD;

            tsk->flags |= PF_NOFREEZE; /* Tell freezer to ignore us: */

            __schedule(false);