diff --git a/exit.c(detailed) b/exit.c(detailed)
new file mode 100644
index 0000000..200167e
--- /dev/null
+++ b/exit.c(detailed)
@@ -0,0 +1,290 @@
+/*
+ *  linux/kernel/exit.c
+ *
+ *  (C) 1991  Linus Torvalds
+ */
+
+#include <errno.h>
+#include <signal.h>
+#include <sys/wait.h>
+
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/tty.h>
+#include <asm/segment.h>
+#include <unistd.h>//
+
+int sys_pause(void);
+int sys_close(int fd);
+
+void* thread_value[4096] = {};//
+
+void release(struct task_struct* p)
+{
+	int i;
+
+	if (!p)
+		return;
+	for (i = 1; i < NR_TASKS; i++)
+		if (task[i] == p) {
+			task[i] = NULL;
+			free_page((long)p);
+			schedule();
+			return;
+		}
+	panic("trying to release non-existent task");
+}
+
+static inline int send_sig(long sig, struct task_struct* p, int priv)
+{
+	if (!p || sig < 1 || sig>32)
+		return -EINVAL;
+	if (priv || (current->euid == p->euid) || suser())
+		p->signal |= (1 << (sig - 1));
+	else
+		return -EPERM;
+	return 0;
+}
+
+static void kill_session(void)
+{
+	struct task_struct** p = NR_TASKS + task;
+
+	while (--p > &FIRST_TASK) {
+		if (*p && (*p)->session == current->session)
+			(*p)->signal |= 1 << (SIGHUP - 1);
+	}
+}
+
+/*
+ * XXX need to check permissions needed to send signals to process
+ * groups, etc. etc.  kill() permissions semantics are tricky!
+ */
+int sys_kill(int pid, int sig)
+{
+	struct task_struct** p = NR_TASKS + task;
+	int err, retval = 0;
+
+	if (!pid) while (--p > &FIRST_TASK) {
+		if (*p && (*p)->pgrp == current->pid)
+			if (err = send_sig(sig, *p, 1))
+				retval = err;
+	}
+	else if (pid > 0) while (--p > &FIRST_TASK) {
+		if (*p && (*p)->pid == pid)
+			if (err = send_sig(sig, *p, 0))
+				retval = err;
+	}
+	else if (pid == -1) while (--p > &FIRST_TASK)
+		if (err = send_sig(sig, *p, 0))
+			retval = err;
+		else while (--p > &FIRST_TASK)
+			if (*p && (*p)->pgrp == -pid)
+				if (err = send_sig(sig, *p, 0))
+					retval = err;
+	return retval;
+}
+
+static void tell_father(int pid)
+{
+	int i;
+
+	if (pid)
+		for (i = 0; i < NR_TASKS; i++) {
+			if (!task[i])
+				continue;
+			if (task[i]->pid != pid)
+				continue;
+			task[i]->signal |= (1 << (SIGCHLD - 1));
+			return;
+		}
+	/* if we don't find any fathers, we just release ourselves */
+	/* This is not really OK. Must change it to make father 1 */
+	printk("BAD BAD - no father found\n\r");
+	release(current);
+}
+
+int do_exit(long code)
+{
+	int i;
+	free_page_tables(get_base(current->ldt[1]), get_limit(0x0f));
+	free_page_tables(get_base(current->ldt[2]), get_limit(0x17));
+	for (i = 0; i < NR_TASKS; i++)
+		if (task[i] && task[i]->father == current->pid) {
+			task[i]->father = 1;
+			if (task[i]->state == TASK_ZOMBIE)
+				/* assumption task[1] is always init */
+				(void)send_sig(SIGCHLD, task[1], 1);
+		}
+	for (i = 0; i < NR_OPEN; i++)
+		if (current->filp[i])
+			sys_close(i);
+	iput(current->pwd);
+	current->pwd = NULL;
+	iput(current->root);
+	current->root = NULL;
+	iput(current->executable);
+	current->executable = NULL;
+	if (current->leader && current->tty >= 0)
+		tty_table[current->tty].pgrp = 0;
+	if (last_task_used_math == current)
+		last_task_used_math = NULL;
+	if (current->leader)
+		kill_session();
+	current->state = TASK_ZOMBIE;
+	current->exit_code = code;
+	tell_father(current->father);
+	schedule();
+	return (-1);	/* just to suppress warnings */
+}
+
+int sys_exit(int error_code)
+{
+	return do_exit((error_code & 0xff) << 8);
+}
+
+int sys_waitpid(pid_t pid, unsigned long* stat_addr, int options)
+{
+	int flag, code;
+	struct task_struct** p;
+
+	verify_area(stat_addr, 4);
+repeat:
+	flag = 0;
+	for (p = &LAST_TASK; p > &FIRST_TASK; --p) {
+		if (!*p || *p == current)
+			continue;
+		if ((*p)->father != current->pid)
+			continue;
+		if (pid > 0) {
+			if ((*p)->pid != pid)
+				continue;
+		}
+		else if (!pid) {
+			if ((*p)->pgrp != current->pgrp)
+				continue;
+		}
+		else if (pid != -1) {
+			if ((*p)->pgrp != -pid)
+				continue;
+		}
+		switch ((*p)->state) {
+		case TASK_STOPPED:
+			if (!(options & WUNTRACED))
+				continue;
+			put_fs_long(0x7f, stat_addr);
+			return (*p)->pid;
+		case TASK_ZOMBIE:
+			current->cutime += (*p)->utime;
+			current->cstime += (*p)->stime;
+			flag = (*p)->pid;
+			code = (*p)->exit_code;
+			release(*p);
+			put_fs_long(code, stat_addr);
+			return flag;
+		default:
+			flag = 1;
+			continue;
+		}
+	}
+	if (flag) {
+		if (options & WNOHANG)
+			return 0;
+		current->state = TASK_INTERRUPTIBLE;
+		schedule();
+		if (!(current->signal &= ~(1 << (SIGCHLD - 1))))
+			goto repeat;
+		else
+			return -EINTR;
+	}
+	return -ECHILD;
+}
+
+int sys_thread_exit(void* value_ptr)               /* ϵͳ����thread_exitʵ�ֺ������ο���do_exit */
+{
+	int i;
+	pthread_t thread;
+
+	free_page_tables(get_base(current->ldt[1]), get_limit(0x0f));
+	free_page_tables(get_base(current->ldt[2]), get_limit(0x17));
+	for (i = 0; i < NR_TASKS; i++)
+		if (task[i] && task[i]->father == current->pid) {
+			task[i]->father = 1;
+			if (task[i]->state == TASK_ZOMBIE)
+				/* assumption task[1] is always init */
+				(void)send_sig(SIGCHLD, task[1], 1);
+		}
+	for (i = 0; i < NR_OPEN; i++)
+		if (current->filp[i])
+			sys_close(i);
+	iput(current->pwd);
+	current->pwd = NULL;
+	iput(current->root);
+	current->root = NULL;
+	iput(current->executable);
+	current->executable = NULL;
+	if (current->leader && current->tty >= 0)
+		tty_table[current->tty].pgrp = 0;
+	if (last_task_used_math == current)
+		last_task_used_math = NULL;
+	if (current->leader)
+		kill_session();
+	current->state = TASK_ZOMBIE;
+	/*********************************************/
+	thread = current->pid;                 /* ��ǰ�߳�ID */
+	thread_value[thread] = value_ptr;      /* �������̵߳ķ���ֵ��¼��thread_value������ */
+	/*********************************************/
+	tell_father(current->father);
+	schedule();
+	return (-1);
+}
+
+int sys_thread_join(pthread_t thread, void** value_ptr)  /* ϵͳ����thread_exitʵ�ֺ������ο���wait_pid */
+{
+	if (thread <= 0 || value_ptr == NULL)
+	{
+		printk("Error:thread joining failed!\n");
+		sys_exit(0);
+	}
+	int flag;
+	struct task_struct** p;
+repeat:
+	flag = 0;
+	/* ����������ĩ�˿�ʼɨ��������������������������Լ��ǵ�ǰ�̵߳����߳��� */
+	for (p = &LAST_TASK; p > &FIRST_TASK; --p)
+	{
+		if (!*p || *p == current) continue;
+		if ((*p)->father != current->pid) continue;
+		/****************************************/
+		if ((*p)->pid != thread) continue;
+		/****************************************/
+		/* ��ʱ�ҵ���p���ǵ�ǰ�̵߳����߳� */
+		switch ((*p)->state)
+		{
+		case TASK_STOPPED:
+			break;
+		case TASK_ZOMBIE:
+			current->cutime += (*p)->utime;
+			current->cstime += (*p)->stime;
+			release(*p);
+			/****************************************/
+			put_fs_long(thread_value[thread], value_ptr); /* ��thread_value�����е�ֵ���� value_ptr��Ҳ���ǽ�����thread_exit�����ķ���ֵ */
+			/****************************************/    /* ��˸��̵߳���sys_thread_join�������ܻ�ȡ���ֵ */
+			return 0;
+		default:
+			flag = 1;
+			break;
+		}
+	}
+	/* flag=1˵���з��ϵȴ�Ҫ������̣߳�����������ֹ����״̬����ʱ�ѵ�ǰ�߳���Ϊ���жϵȴ�״̬�����µ��ȣ��ظ�ִ�� */
+	if (flag) {
+		current->state = TASK_INTERRUPTIBLE;
+		schedule();
+		if (!(current->signal &= ~(1 << (SIGCHLD - 1))))
+			goto repeat;
+		else
+			return -EINTR;
+	}
+	return -ECHILD;
+}
+