add exercise of lab5 spoc discussion

related_info/lab5/lab5-spoc-discuss/kern/sync/sync.h

@@ -0,0 +1,57 @@
+#ifndef __KERN_SYNC_SYNC_H__
+#define __KERN_SYNC_SYNC_H__
+
+#include <x86.h>
+#include <intr.h>
+#include <mmu.h>
+#include <assert.h>
+#include <atomic.h>
+#include <sched.h>
+
+static inline bool
+__intr_save(void) {
+    if (read_eflags() & FL_IF) {
+        intr_disable();
+        return 1;
+    }
+    return 0;
+}
+
+static inline void
+__intr_restore(bool flag) {
+    if (flag) {
+        intr_enable();
+    }
+}
+
+#define local_intr_save(x)      do { x = __intr_save(); } while (0)
+#define local_intr_restore(x)   __intr_restore(x);
+
+typedef volatile bool lock_t;
+
+static inline void
+lock_init(lock_t *lock) {
+    *lock = 0;
+}
+
+static inline bool
+try_lock(lock_t *lock) {
+    return !test_and_set_bit(0, lock);
+}
+
+static inline void
+lock(lock_t *lock) {
+    while (!try_lock(lock)) {
+        schedule();
+    }
+}
+
+static inline void
+unlock(lock_t *lock) {
+    if (!test_and_clear_bit(0, lock)) {
+        panic("Unlock failed.\n");
+    }
+}
+
+#endif /* !__KERN_SYNC_SYNC_H__ */
+