From 18ef8d77b81d5ffa60a24e1c5fa8979c65698847 Mon Sep 17 00:00:00 2001
From: Zhiyuan Shao <zyshao@hust.edu.cn>
Date: Mon, 8 May 2023 15:30:33 +0800
Subject: [PATCH] init commit of lab3_challenge1

---
 LICENSE.txt               |  6 ++++--
 Makefile                  |  2 +-
 user/app_two_long_loops.c | 28 ----------------------------
 user/app_wait.c           | 31 +++++++++++++++++++++++++++++++
 4 files changed, 36 insertions(+), 31 deletions(-)
 delete mode 100644 user/app_two_long_loops.c
 create mode 100644 user/app_wait.c

diff --git a/LICENSE.txt b/LICENSE.txt
index ffe4849..0aba838 100644
--- a/LICENSE.txt
+++ b/LICENSE.txt
@@ -4,8 +4,10 @@ Copyright License
 The PKE software is:
 
 Copyright (c) 2021, Zhiyuan Shao (zyshao@hust.edu.cn), 
-                    Yi Gui (gy163email@163.com), 
-                    Yan Jiao (773709579@qq.com),
+                    Ziming Yuan (1223962053@qq.com),
+                    Yixin Song (yixinsong@hust.edu.cn),
+                    Boyang Li (liboyang_hust@163.com),
+                    Wenzhuo Liu (mgt@oi-wiki.org)
                    Huazhong University of Science and Technology
 
 Permission is hereby granted, free of charge, to any person obtaining
diff --git a/Makefile b/Makefile
index 2dde5bf..598a3e3 100644
--- a/Makefile
+++ b/Makefile
@@ -70,7 +70,7 @@ USER_OBJS  		:= $(addprefix $(OBJ_DIR)/, $(patsubst %.c,%.o,$(USER_CPPS)))
 
 
 
-USER_TARGET 	:= $(OBJ_DIR)/app_two_long_loops
+USER_TARGET 	:= $(OBJ_DIR)/app_wait
 #------------------------targets------------------------
 $(OBJ_DIR):
 	@-mkdir -p $(OBJ_DIR)	
diff --git a/user/app_two_long_loops.c b/user/app_two_long_loops.c
deleted file mode 100644
index 2568485..0000000
--- a/user/app_two_long_loops.c
+++ /dev/null
@@ -1,28 +0,0 @@
-/*
- * The application of lab3_3.
- * parent and child processes never give up their processor during execution.
- */
-
-#include "user/user_lib.h"
-#include "util/types.h"
-
-int main(void) {
-  uint64 pid = fork();
-  uint64 rounds = 100000000;
-  uint64 interval = 10000000;
-  uint64 a = 0;
-  if (pid == 0) {
-    printu("Child: Hello world! \n");
-    for (uint64 i = 0; i < rounds; ++i) {
-      if (i % interval == 0) printu("Child running %ld \n", i);
-    }
-  } else {
-    printu("Parent: Hello world! \n");
-    for (uint64 i = 0; i < rounds; ++i) {
-      if (i % interval == 0) printu("Parent running %ld \n", i);
-    }
-  }
-
-  exit(0);
-  return 0;
-}
diff --git a/user/app_wait.c b/user/app_wait.c
new file mode 100644
index 0000000..eeea575
--- /dev/null
+++ b/user/app_wait.c
@@ -0,0 +1,31 @@
+/*
+ * This app fork a child process, and the child process fork a grandchild process.
+ * every process waits for its own child exit then prints.                     
+ * Three processes also write their own global variables "flag"
+ * to different values.
+ */
+
+#include "user/user_lib.h"
+#include "util/types.h"
+
+int flag;
+int main(void) {
+    flag = 0;
+    int pid = fork();
+    if (pid == 0) {
+        flag = 1;
+        pid = fork();
+        if (pid == 0) {
+            flag = 2;
+            printu("Grandchild process end, flag = %d.\n", flag);
+        } else {
+            wait(pid);
+            printu("Child process end, flag = %d.\n", flag);
+        }
+    } else {
+        wait(-1);
+        printu("Parent process end, flag = %d.\n", flag);
+    }
+    exit(0);
+    return 0;
+}