Add the new other type of lock

06-Spinlock/lock.c

@@ -1,5 +1,26 @@
 #include "os.h"
 
+void lock_init(lock_t *lock)
+{
+  lock->locked = 0;
+}
+
+void lock_acquire(lock_t *lock)
+{
+  for (;;)
+  {
+    if (!atomic_swap(lock))
+    {
+      break;
+    }
+  }
+}
+
+void lock_free(lock_t *lock)
+{
+  lock->locked = 0;
+}
+
 void spinlock_lock()
 {
   w_mstatus(r_mstatus() & ~MSTATUS_MIE);
@@ -8,4 +29,4 @@ void spinlock_lock()
 void spinlock_unlock()
 {
   w_mstatus(r_mstatus() | MSTATUS_MIE);
-}
+}

06-Spinlock/os.h

@@ -12,4 +12,17 @@ extern int os_main(void);
 extern void spinlock_lock();
 extern void spinlock_unlock();
 
+typedef struct lock
+{
+  int locked;
+} lock_t;
+
+extern int atomic_swap(lock_t *);
+
+extern void lock_init(lock_t *lock);
+
+extern void lock_acquire(lock_t *lock);
+
+extern void lock_free(lock_t *lock);
+
 #endif

06-Spinlock/sys.s

@@ -121,6 +121,13 @@ sys_switch:
         ctx_load a1  # a1 => struct context *new
         ret          # pc=ra; swtch to new task (new->ra)
 
+.globl atomic_swap
+.align 4
+atomic_swap:
+        li a5, 1
+        amoswap.w.aq a5, a5, 0(a0)
+        mv a0, a5
+        ret
 
 .globl trap_vector
 # the trap vector base address must always be aligned on a 4-byte boundary

06-Spinlock/user.c

@@ -2,6 +2,8 @@
 
 int shared_var = 500;
 
+lock_t lock;
+
 void user_task0(void)
 {
 	lib_puts("Task0: Created!\n");
@@ -29,18 +31,33 @@ void user_task2(void)
 	{
 		for (int i = 0; i < 50; i++)
 		{
-			spinlock_lock();
+			lock_acquire(&lock);
 			shared_var++;
-			spinlock_unlock();
+			lock_free(&lock);
+			lib_delay(100);
 		}
-		lib_delay(6000);
 		lib_printf("The value of shared_var is: %d \n", shared_var);
 	}
 }
 
+void user_task3(void)
+{
+	lib_puts("Task3: Created!\n");
+	while (1)
+	{
+		lib_puts("Tryin to get the lock... \n");
+		lock_acquire(&lock);
+		lib_puts("Get the lock!\n");
+		lock_free(&lock);
+		lib_delay(1000);
+	}
+}
+
 void user_init()
 {
+	lock_init(&lock);
 	task_create(&user_task0);
 	task_create(&user_task1);
 	task_create(&user_task2);
+	task_create(&user_task3);
 }

doc/tw/06-Spinlock.md

@@ -0,0 +1 @@
+# 06-Spinlock -- RISC-V 的嵌入式作業系統