LAB 4 IS DONE.

lab/kern/spinlock.h

@@ -0,0 +1,48 @@
+#ifndef JOS_INC_SPINLOCK_H
+#define JOS_INC_SPINLOCK_H
+
+#include <inc/types.h>
+
+// Comment this to disable spinlock debugging
+#define DEBUG_SPINLOCK
+
+// Mutual exclusion lock.
+struct spinlock {
+	unsigned locked;       // Is the lock held?
+
+#ifdef DEBUG_SPINLOCK
+	// For debugging:
+	char *name;            // Name of lock.
+	struct CpuInfo *cpu;   // The CPU holding the lock.
+	uintptr_t pcs[10];     // The call stack (an array of program counters)
+	                       // that locked the lock.
+#endif
+};
+
+void __spin_initlock(struct spinlock *lk, char *name);
+void spin_lock(struct spinlock *lk);
+void spin_unlock(struct spinlock *lk);
+
+#define spin_initlock(lock)   __spin_initlock(lock, #lock)
+
+extern struct spinlock kernel_lock;
+
+static inline void
+lock_kernel(void)
+{
+	spin_lock(&kernel_lock);
+}
+
+static inline void
+unlock_kernel(void)
+{
+	spin_unlock(&kernel_lock);
+
+	// Normally we wouldn't need to do this, but QEMU only runs
+	// one CPU at a time and has a long time-slice.  Without the
+	// pause, this CPU is likely to reacquire the lock before
+	// another CPU has even been given a chance to acquire it.
+	asm volatile("pause");
+}
+
+#endif