init commit of lab3_challenge2

LICENSE.txt

@@ -3,9 +3,10 @@ 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),
+Copyright (c) 2021, Zhiyuan Shao (zyshao@hust.edu.cn),
+                    Ziming Yuan (1223962053@qq.com),
+                    Yixin Song (yixinsong@hust.edu.cn),
+                    Boyang Li (liboyang_hust@163.com)
                    Huazhong University of Science and Technology
 
 Permission is hereby granted, free of charge, to any person obtaining

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_semaphore
 #------------------------targets------------------------
 $(OBJ_DIR):
 	@-mkdir -p $(OBJ_DIR)	

user/app_semaphore.c

@@ -0,0 +1,30 @@
+/*
+* This app create two child process.
+* Use semaphores to control the order of
+* the main process and two child processes print info. 
+*/
+#include "user/user_lib.h"
+#include "util/types.h"
+
+int main(void) {
+    int main_sem, child_sem[2];
+    main_sem = sem_new(1); 
+    for (int i = 0; i < 2; i++) child_sem[i] = sem_new(0);
+    int pid = fork();
+    if (pid == 0) {
+        pid = fork();
+        for (int i = 0; i < 10; i++) {
+            sem_P(child_sem[pid == 0]);
+            printu("Child%d print %d\n", pid == 0, i);
+            if (pid != 0) sem_V(child_sem[1]); else sem_V(main_sem);
+        }
+    } else {
+        for (int i = 0; i < 10; i++) {
+            sem_P(main_sem);
+            printu("Parent print %d\n", i);
+            sem_V(child_sem[0]);
+        }
+    }
+    exit(0);
+    return 0;
+}

user/app_two_long_loops.c

@@ -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;
-}