alarm task finished

kernel/trap.c

@@ -77,8 +77,15 @@ usertrap(void)
     exit(-1);
 
   // give up the CPU if this is a timer interrupt.
-  if(which_dev == 2)
-    yield();
+  if(which_dev == 2){
+    p->inter_cnt++;
+    if (p->inter_cnt == p->alarm_cnt && 0 < p->alarm_cnt) {
+      *p->pre_trapframe = *p->trapframe;
+      p->trapframe->epc = p->handler;
+    } else {
+      yield();
+    }
+  }
 
   usertrapret();
 }