diff --git a/kern/conf/DUMBVM b/kern/conf/DUMBVM
index 7862c64..6cabdba 100644
--- a/kern/conf/DUMBVM
+++ b/kern/conf/DUMBVM
@@ -30,3 +30,6 @@ options sfs			# Always use the file system
 #options netfs			# You might write this as a project.
 
 options dumbvm			# Chewing gum and baling wire.
+
+#options semlock     #locks with semaphores
+options wchanlock    #locks with wchans
diff --git a/kern/conf/conf.kern b/kern/conf/conf.kern
index 1e57da3..b5d5821 100644
--- a/kern/conf/conf.kern
+++ b/kern/conf/conf.kern
@@ -444,6 +444,9 @@ optfile net	test/nettest.c
 defoption hello
 optfile hello   main/hello.c
 
+defoption semlock
+defoption wchanlock
+
 # LAB2
 file    syscall/file_syscalls.c
 file    syscall/proc_syscalls.c
diff --git a/kern/include/synch.h b/kern/include/synch.h
index fee3b07..c80c62d 100644
--- a/kern/include/synch.h
+++ b/kern/include/synch.h
@@ -37,6 +37,9 @@
 
 #include <spinlock.h>
 
+#include "opt-semlock.h"
+#include "opt-wchanlock.h"
+
 /*
  * Dijkstra-style semaphore.
  *
@@ -72,10 +75,19 @@ void V(struct semaphore *);
  * The name field is for easier debugging. A copy of the name is
  * (should be) made internally.
  */
+
 struct lock {
         char *lk_name;
+        volatile struct thread *owner;
+#if OPT_SEMLOCK
+        struct semaphore *sem;
+#elif OPT_WCHANLOCK
+        struct spinlock slk;
+        struct wchan *wchan;
+#else
         // add what you need here
         // (don't forget to mark things volatile as needed)
+#endif
 };
 
 struct lock *lock_create(const char *name);
diff --git a/kern/thread/synch.c b/kern/thread/synch.c
index d083f4b..bc64eac 100644
--- a/kern/thread/synch.c
+++ b/kern/thread/synch.c
@@ -156,6 +156,24 @@ lock_create(const char *name)
 
         // add stuff here as needed
 
+#if OPT_SEMLOCK
+        lock->sem = sem_create(name, 1);
+        if (lock->sem == NULL) {
+		kfree(lock->lk_name);
+		kfree(lock);
+                return NULL;
+        }
+#elif OPT_WCHANLOCK
+	lock->wchan = wchan_create(lock->lk_name);
+	if (lock->wchan == NULL) {
+		kfree(lock->lk_name);
+		kfree(lock);
+		return NULL;
+	}
+        spinlock_init(&lock->slk);
+#endif
+
+        lock->owner = NULL;
         return lock;
 }
 
@@ -167,6 +185,12 @@ lock_destroy(struct lock *lock)
         // add stuff here as needed
 
         kfree(lock->lk_name);
+#if OPT_SEMLOCK
+        sem_destroy(lock->sem);
+#elif OPT_WCHANLOCK
+        wchan_destroy(lock->wchan);
+        spinlock_cleanup(&lock->slk);
+#endif
         kfree(lock);
 }
 
@@ -175,7 +199,19 @@ lock_acquire(struct lock *lock)
 {
         // Write this
 
-        (void)lock;  // suppress warning until code gets written
+#if OPT_SEMLOCK
+        P(lock->sem);
+        lock->owner = curthread;
+#elif OPT_WCHANLOCK
+        spinlock_acquire(&lock->slk);
+        while (lock->owner != NULL) {
+		wchan_sleep(lock->wchan, &lock->slk);
+        }
+        lock->owner = curthread;
+        spinlock_release(&lock->slk);
+#else
+        lock->owner = curthread;
+#endif
 }
 
 void
@@ -183,17 +219,36 @@ lock_release(struct lock *lock)
 {
         // Write this
 
-        (void)lock;  // suppress warning until code gets written
+        KASSERT(lock != NULL);
+        KASSERT(lock_do_i_hold(lock));
+#if OPT_SEMLOCK
+        lock->owner = NULL;
+        V(lock->sem);
+#elif OPT_WCHANLOCK
+        spinlock_acquire(&lock->slk);
+        lock->owner = NULL;
+	wchan_wakeall(lock->wchan, &lock->slk);
+        spinlock_release(&lock->slk);
+#else
+        lock->owner = NULL;
+#endif
 }
 
 bool
 lock_do_i_hold(struct lock *lock)
 {
         // Write this
+        KASSERT(lock != NULL);
+#if OPT_WCHANLOCK
+        bool ret = true;
+        spinlock_acquire(&lock->slk);
+        ret = lock->owner == curthread;
+        spinlock_release(&lock->slk);
+        return ret; // dummy until code gets written
+#else
+        return lock->owner == curthread;
+#endif
 
-        (void)lock;  // suppress warning until code gets written
-
-        return true; // dummy until code gets written
 }
 
 ////////////////////////////////////////////////////////////