diff --git a/l10/l10-handout.txt b/l10/l10-handout.txt
index 4502406..54421b1 100644
--- a/l10/l10-handout.txt
+++ b/l10/l10-handout.txt
@@ -108,7 +108,8 @@ Class 10
 
 	Moral of the above paragraph: if you're implementing a
 	concurrency primitive, read the processor's documentation about
-	how loads and stores get sequenced.
+	how loads and stores get sequenced (chapter 8 in current
+	architecture manual).
 
 	The spinlock above is great for some things, not so great for
 	others. The main problem is that it *busy waits*: it spins,
@@ -302,7 +303,7 @@ Class 10
 		 buffer [in] = nextProduced;
 		 in = (in + 1) % BUFFER_SIZE;
 		 count++;
-		 cond_signal(&nonempty);
+		 cond_signal(&nonempty, &mutex);
 		 release(&mutex);
 	     }
 	 }
@@ -317,7 +318,7 @@ Class 10
 		 nextConsumed = buffer[out];
 		 out = (out + 1) % BUFFER_SIZE;
 		 count--;
-		 cond_signal(&nonfull);
+		 cond_signal(&nonfull, &mutex);
 		 release(&mutex);
 
 		 /* next line abstractly consumes the item */
@@ -451,6 +452,7 @@ Class 10
 	--count;
 	cond_signal(&nonfull, &mutex);
 	mutex.release();
+	return ret;
     }
 
     int main(int, char**)