1 files changed, 58 insertions, 0 deletions
diff --git a/src/tests/threads/alarm-priority.c b/src/tests/threads/alarm-priority.c
new file mode 100644
index 0000000..2288ff6
--- /dev/null
+++ b/src/tests/threads/alarm-priority.c
@@ -0,0 +1,58 @@
+/* Checks that when the alarm clock wakes up threads, the
+   higher-priority threads run first. */
+
+#include <stdio.h>
+#include "tests/threads/tests.h"
+#include "threads/init.h"
+#include "threads/malloc.h"
+#include "threads/synch.h"
+#include "threads/thread.h"
+#include "devices/timer.h"
+
+static thread_func alarm_priority_thread;
+static int64_t wake_time;
+static struct semaphore wait_sema;
+
+void
+test_alarm_priority (void) 
+{
+  int i;
+  
+  /* This test does not work with the MLFQS. */
+  ASSERT (!thread_mlfqs);
+
+  wake_time = timer_ticks () + 5 * TIMER_FREQ;
+  sema_init (&wait_sema, 0);
+  
+  for (i = 0; i < 10; i++) 
+    {
+      int priority = PRI_DEFAULT - (i + 5) % 10 - 1;
+      char name[16];
+      snprintf (name, sizeof name, "priority %d", priority);
+      thread_create (name, priority, alarm_priority_thread, NULL);
+    }
+
+  thread_set_priority (PRI_MIN);
+
+  for (i = 0; i < 10; i++)
+    sema_down (&wait_sema);
+}
+
+static void
+alarm_priority_thread (void *aux UNUSED) 
+{
+  /* Busy-wait until the current time changes. */
+  int64_t start_time = timer_ticks ();
+  while (timer_elapsed (start_time) == 0)
+    continue;
+
+  /* Now we know we're at the very beginning of a timer tick, so
+     we can call timer_sleep() without worrying about races
+     between checking the time and a timer interrupt. */
+  timer_sleep (wake_time - timer_ticks ());
+
+  /* Print a message on wake-up. */
+  msg ("Thread %s woke up.", thread_name ());
+
+  sema_up (&wait_sema);
+}