1 files changed, 114 insertions, 0 deletions
diff --git a/src/tests/threads/priority-donate-chain.c b/src/tests/threads/priority-donate-chain.c
new file mode 100644
index 0000000..3ffabca
--- /dev/null
+++ b/src/tests/threads/priority-donate-chain.c
@@ -0,0 +1,114 @@
+/* The main thread set its priority to PRI_MIN and creates 7 threads 
+   (thread 1..7) with priorities PRI_MIN + 3, 6, 9, 12, ...
+   The main thread initializes 8 locks: lock 0..7 and acquires lock 0.
+
+   When thread[i] starts, it first acquires lock[i] (unless i == 7.)
+   Subsequently, thread[i] attempts to acquire lock[i-1], which is held by
+   thread[i-1], except for lock[0], which is held by the main thread.
+   Because the lock is held, thread[i] donates its priority to thread[i-1],
+   which donates to thread[i-2], and so on until the main thread
+   receives the donation.
+
+   After threads[1..7] have been created and are blocked on locks[0..7],
+   the main thread releases lock[0], unblocking thread[1], and being
+   preempted by it.
+   Thread[1] then completes acquiring lock[0], then releases lock[0],
+   then releases lock[1], unblocking thread[2], etc.
+   Thread[7] finally acquires & releases lock[7] and exits, allowing 
+   thread[6], then thread[5] etc. to run and exit until finally the 
+   main thread exits.
+
+   In addition, interloper threads are created at priority levels
+   p = PRI_MIN + 2, 5, 8, 11, ... which should not be run until the 
+   corresponding thread with priority p + 1 has finished.
+  
+   Written by Godmar Back <gback@cs.vt.edu> */ 
+
+#include <stdio.h>
+#include "tests/threads/tests.h"
+#include "threads/init.h"
+#include "threads/synch.h"
+#include "threads/thread.h"
+
+#define NESTING_DEPTH 8
+
+struct lock_pair
+  {
+    struct lock *second;
+    struct lock *first;
+  };
+
+static thread_func donor_thread_func;
+static thread_func interloper_thread_func;
+
+void
+test_priority_donate_chain (void) 
+{
+  int i;  
+  struct lock locks[NESTING_DEPTH - 1];
+  struct lock_pair lock_pairs[NESTING_DEPTH];
+
+  /* This test does not work with the MLFQS. */
+  ASSERT (!thread_mlfqs);
+
+  thread_set_priority (PRI_MIN);
+
+  for (i = 0; i < NESTING_DEPTH - 1; i++)
+    lock_init (&locks[i]);
+
+  lock_acquire (&locks[0]);
+  msg ("%s got lock.", thread_name ());
+
+  for (i = 1; i < NESTING_DEPTH; i++)
+    {
+      char name[16];
+      int thread_priority;
+
+      snprintf (name, sizeof name, "thread %d", i);
+      thread_priority = PRI_MIN + i * 3;
+      lock_pairs[i].first = i < NESTING_DEPTH - 1 ? locks + i: NULL;
+      lock_pairs[i].second = locks + i - 1;
+
+      thread_create (name, thread_priority, donor_thread_func, lock_pairs + i);
+      msg ("%s should have priority %d.  Actual priority: %d.",
+          thread_name (), thread_priority, thread_get_priority ());
+
+      snprintf (name, sizeof name, "interloper %d", i);
+      thread_create (name, thread_priority - 1, interloper_thread_func, NULL);
+    }
+
+  lock_release (&locks[0]);
+  msg ("%s finishing with priority %d.", thread_name (),
+                                         thread_get_priority ());
+}
+
+static void
+donor_thread_func (void *locks_) 
+{
+  struct lock_pair *locks = locks_;
+
+  if (locks->first)
+    lock_acquire (locks->first);
+
+  lock_acquire (locks->second);
+  msg ("%s got lock", thread_name ());
+
+  lock_release (locks->second);
+  msg ("%s should have priority %d. Actual priority: %d", 
+        thread_name (), (NESTING_DEPTH - 1) * 3,
+        thread_get_priority ());
+
+  if (locks->first)
+    lock_release (locks->first);
+
+  msg ("%s finishing with priority %d.", thread_name (),
+                                         thread_get_priority ());
+}
+
+static void
+interloper_thread_func (void *arg_ UNUSED)
+{
+  msg ("%s finished.", thread_name ());
+}
+
+// vim: sw=2