Initial Upload

spinlock.h

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+// Mutual exclusion lock.
+struct spinlock {
+    uint locked;       // Is the lock held?
+
+    // For debugging:
+    char *name;        // Name of lock.
+    struct cpu *cpu;   // The cpu holding the lock.
+    uint pcs[10];      // The call stack (an array of program counters)
+                       // that locked the lock.
+};
+