disable interrupts when queueing threadslab2

1 files changed, 5 insertions, 0 deletions

diff --git a/src/devices/timer.c b/src/devices/timer.c
index 856a14e..aea6aa2 100644
--- a/src/devices/timer.c
+++ b/src/devices/timer.c
@@ -114,6 +114,9 @@ timer_sleep (int64_t ticks)
   new_waiting_thread.tick_target = start + ticks;
   sema_init (&new_waiting_thread.sema, 0);
 
+  // disable interrupts so the timer interrupt handler can't modify the list
+  enum intr_level old_level = intr_disable ();
+
   struct list_elem *before = list_begin (&waiting_threads);
   while (before != list_end (&waiting_threads)) {
     struct list_elem *next = list_next (before);
@@ -125,6 +128,8 @@ timer_sleep (int64_t ticks)
   }
   list_insert (before, &new_waiting_thread.elem);
 
+  intr_set_level (old_level);
+
   sema_down (&new_waiting_thread.sema);
 }