diff --git a/kern/fork.c b/kern/fork.c
index 5165f2b..b42b4d0 100644
--- a/kern/fork.c
+++ b/kern/fork.c
@@ -125,7 +125,7 @@ kern_fork(PROCESS_0 *p_fa)
 	if (proc_child == NULL) {
 		// NO hell. no free proc_table found. 
 		xchg(&p_fa->lock, 0);
-		return ENOMEM;
+		return -EAGAIN;
 	}
 	PROCESS_0 *p_child = &proc_child->pcb;
 	// 再之后你需要做的是好好阅读一下pcb的数据结构，搞明白结构体中每个成员的语义
diff --git a/kern/main.c b/kern/main.c
index 87e6057..d0f3df4 100644
--- a/kern/main.c
+++ b/kern/main.c
@@ -40,7 +40,7 @@ void kernel_main(void)
 	p_proc->priority = p_proc->ticks = 1;
 	// 在实现了exec系统调用后main函数的负担就少了
 	// 只需要调用一个函数接口就能实现进程的加载
-	if (do_exec("testfork.bin") < 0)
+	if (do_exec("initproc.bin") < 0)
 		panic("init process failed");
 	// 切换tss
 	tss.esp0 = (u32)(&p_proc->user_regs + 1);
diff --git a/kern/wait.c b/kern/wait.c
index 16fd9bf..94992f6 100644
--- a/kern/wait.c
+++ b/kern/wait.c
@@ -1,9 +1,23 @@
 #include <assert.h>
 #include <mmu.h>
+#include <errno.h>
+#include <x86.h>
 
 #include <kern/syscall.h>
 #include <kern/wait.h>
+#include <kern/process.h>
+#include <kern/pmap.h>
+#include <kern/sche.h>
+#include <kern/kmalloc.h>
 
+/*
+The wait() system call suspends execution of the calling thread
+    until one of its children terminates. 
+RETURN VALUE
+on success, returns the process ID of the terminated child; 
+on failure, -1 is returned.
+! however the testwait.bin expects a valued return other than simply -1
+*/
 ssize_t
 kern_wait(int *wstatus)
 {
@@ -13,21 +27,82 @@ kern_wait(int *wstatus)
 
 	// 在实现之前你必须得读一遍文档`man 2 wait`
 	// 了解到wait大概要做什么
-	panic("Unimplement! Read The F**king Manual");
+	// panic("Unimplement! Read The F**king Manual");
 
 	// 当然读文档是一方面，最重要的还是代码实现
 	// wait系统调用与exit系统调用关系密切，所以在实现wait之前需要先读一遍exit为好
 	// 可能读完exit的代码你可能知道wait该具体做什么了
-	panic("Unimplement! Read The F**king Source Code");
+	// panic("Unimplement! Read The F**king Source Code");
 
+	PROCESS_0 *p_fa = &p_proc_ready->pcb;
+	int child_pid = -1;
+again:
+	while (xchg(&p_fa->lock, 1) == 1)
+		schedule();
+	struct son_node* p_son = p_fa->fork_tree.sons;
+	if (p_son == NULL) {
+		xchg(&p_fa->lock, 0);
+		return -ECHILD;
+	}
+	assert(p_son->pre == NULL); // make sure it is the head of the list
+	while (p_son != NULL) {
+		if (p_son->p_son->statu == ZOMBIE) {
+/*
+struct s_proc {
+user_regs; // let it be
+kern_regs; // let it be
+lock;  // get and release before kfree
+statu; // set to IDLE
+pid; // keep it util return 
+cr3; // let it be
+page_list; // recycle it
+exit_code; // set to wstatus
+priority; // let it be
+ticks; // let it be
+fork_tree; // already cleared
+};
+*/
+			while (xchg(&p_son->p_son->lock, 1) == 1)
+				schedule();
+			// just use this value, which is '(status & 0xFF) << 8' in exit.c::do_exit
+			if (wstatus != NULL)
+				*wstatus = p_son->p_son->exit_code;
+			// recycle_pages in pmap.c
+			recycle_pages(p_son->p_son->page_list);
+			// free it in proc table, 'cause in fork I judge free by statu
+			p_son->p_son->statu = IDLE; 
+			// remove p_son from p_fa's son list
+			if (p_son->pre != NULL) {
+				p_son->pre->nxt = p_son->nxt;
+			}
+			else {
+				p_fa->fork_tree.sons = p_son->nxt;
+			}
+			if (p_son->nxt != NULL) {
+				p_son->nxt->pre = p_son->pre;
+			}
+			// keep p_son's pid for retval, 'cause the pointer will get freed before return
+			child_pid = p_son->p_son->pid;
+			xchg(&p_son->p_son->lock, 0);
+			kfree(p_son);
+			goto done;
+		}
+		p_son = p_son->nxt;
+	}
+	p_fa->statu = SLEEP;
+	xchg(&p_fa->lock, 0);
+	schedule();
+	goto again;
 	// 接下来就是你自己的实现了，我们在设计的时候这段代码不会有太大问题
 	// 在实现完后你任然要对自己来个灵魂拷问
 	// 1. 上锁上了吗？所有临界情况都考虑到了吗？（永远要相信有各种奇奇怪怪的并发问题）
 	// 2. 所有错误情况都判断到了吗？错误情况怎么处理？（RTFM->`man 2 wait`）
 	// 3. 是否所有的资源都正确回收了？
 	// 4. 你写的代码真的符合wait语义吗？
-	panic("Unimplement! soul torture");
-	return 0;
+done:
+	xchg(&p_fa->lock, 0);
+	// panic("Unimplement! soul torture");
+	return child_pid;
 }
 
 ssize_t