fastcall NORET_TYPE void do_exit(long code)

{

	struct task_struct *tsk = current;

	int group_dead;

	profile_task_exit(tsk);

	WARN_ON(atomic_read(&tsk->fs_excl));

	if (unlikely(in_interrupt()))

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

	if (unlikely(!tsk->pid))

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

	if (unlikely(current->ptrace & PT_TRACE_EXIT)) {

		current->ptrace_message = code;

		ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP);

	}

	/*

	 * We're taking recursive faults here in do_exit. Safest is to just

	 * leave this task alone and wait for reboot.

	 */

	if (unlikely(tsk->flags & PF_EXITING)) {

		printk(KERN_ALERT

			"Fixing recursive fault but reboot is needed!\n");

		/*

		 * We can do this unlocked here. The futex code uses

		 * this flag just to verify whether the pi state

		 * cleanup has been done or not. In the worst case it

		 * loops once more. We pretend that the cleanup was

		 * done as there is no way to return. Either the

		 * OWNER_DIED bit is set by now or we push the blocked

		 * task into the wait for ever nirwana as well.

		 */

		tsk->flags |= PF_EXITPIDONE;

		if (tsk->io_context)

			exit_io_context();

		set_current_state(TASK_UNINTERRUPTIBLE);

		schedule();

	}

	tsk->flags |= PF_EXITING; //更改标志位， 表示进程正在退出

	/*

	 * tsk->flags are checked in the futex code to protect against

	 * an exiting task cleaning up the robust pi futexes.

	 */

	smp_mb();

	spin_unlock_wait(&tsk->pi_lock);

	if (unlikely(in_atomic()))

		printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",

				current->comm, task_pid_nr(current),

				preempt_count());

	acct_update_integrals(tsk);

	if (tsk->mm) {

		update_hiwater_rss(tsk->mm);

		update_hiwater_vm(tsk->mm);

	}

	group_dead = atomic_dec_and_test(&tsk->signal->live);

	if (group_dead) {

		exit_child_reaper(tsk);

		hrtimer_cancel(&tsk->signal->real_timer);

		exit_itimers(tsk->signal);

	}

	acct_collect(code, group_dead);

#ifdef CONFIG_FUTEX

	if (unlikely(tsk->robust_list))

		exit_robust_list(tsk);

#ifdef CONFIG_COMPAT

	if (unlikely(tsk->compat_robust_list))

		compat_exit_robust_list(tsk);

#endif

#endif

	if (group_dead)

		tty_audit_exit();

	if (unlikely(tsk->audit_context))

		audit_free(tsk);

	tsk->exit_code = code;

	taskstats_exit(tsk, group_dead);

	exit_mm(tsk); //释放 mm_struct

	if (group_dead)

		acct_process();

	//释放各种资源

	exit_sem(tsk);

	__exit_files(tsk);

	__exit_fs(tsk);

	check_stack_usage();

	exit_thread();

	cgroup_exit(tsk, 1);

	exit_keys(tsk);

	if (group_dead && tsk->signal->leader)

		disassociate_ctty(1);

	//减少模块的引用计数

	module_put(task_thread_info(tsk)->exec_domain->module);

	if (tsk->binfmt)

		module_put(tsk->binfmt->module);

	proc_exit_connector(tsk);

	//1 更新进程的亲属关系， 在进程组里为子进程重新找parent，如果找不到，则设parent为init

	//2  给父进程发送相应的信号

	exit_notify(tsk);

#ifdef CONFIG_NUMA

	mpol_free(tsk->mempolicy);

	tsk->mempolicy = NULL;

#endif

#ifdef CONFIG_FUTEX

	/*

	 * This must happen late, after the PID is not

	 * hashed anymore:

	 */

	if (unlikely(!list_empty(&tsk->pi_state_list)))

		exit_pi_state_list(tsk);

	if (unlikely(current->pi_state_cache))

		kfree(current->pi_state_cache);

#endif

	/*

	 * Make sure we are holding no locks:

	 */

	debug_check_no_locks_held(tsk);

	/*

	 * We can do this unlocked here. The futex code uses this flag

	 * just to verify whether the pi state cleanup has been done

	 * or not. In the worst case it loops once more.

	 */

	tsk->flags |= PF_EXITPIDONE; //进程退出已经完成了，设置PF_EXITPIDONE

	if (tsk->io_context)

		exit_io_context();

	if (tsk->splice_pipe)

		__free_pipe_info(tsk->splice_pipe);

	preempt_disable();

	/* causes final put_task_struct in finish_task_switch(). */

	tsk->state = TASK_DEAD; //设置进程的状态为TASK_DEAD

	schedule(); ////调度另一个进程运行

	BUG();

	/* Avoid "noreturn function does return".  */

	for (;;)

		cpu_relax();	/* For when BUG is null */

}