Merge branch 'master' into 'BSD-merged', fixing merge conflicts

# Conflicts:
#   src/threads/thread.c

src/threads/thread.c

@@ -78,6 +78,8 @@ static bool thread_priority_less (const struct list_elem *a,
 static void schedule (void);
 void thread_schedule_tail (struct thread *prev);
 static tid_t allocate_tid (void);
+static bool donor_priority_less (const struct list_elem *a_,
+                                 const struct list_elem *b_, void *aux UNUSED);
 
 /* Initializes the threading system by transforming the code
    that's currently running into a thread.  This can't work in
@@ -252,6 +254,7 @@ thread_create (const char *name, int priority,
 
   /* Add to run queue. */
   thread_unblock (t);
+  thread_yield ();
 
   return tid;
 }
@@ -289,10 +292,13 @@ thread_unblock (struct thread *t)
 
   old_level = intr_disable ();
   ASSERT (t->status == THREAD_BLOCKED);
+
   if (thread_mlfqs)
     list_insert_ordered (&ready_list, &t->elem, thread_priority_less, NULL);
   else
-    list_push_back (&ready_list, &t->elem);
+    /* Insert the thread back into the ready list in priority order. */
+    list_insert_ordered(&ready_list, &t->elem, priority_more, NULL);
+
   t->status = THREAD_READY;
   intr_set_level (old_level);
 }
@@ -362,14 +368,17 @@ thread_yield (void)
   ASSERT (!intr_context ());
 
   old_level = intr_disable ();
+
   if (cur != idle_thread)
     {
       if (thread_mlfqs)
         list_insert_ordered (&ready_list, &cur->elem, thread_priority_less,
                              NULL);
       else
-        list_push_back (&ready_list, &cur->elem);
+        /* Insert the thread back into the ready list in priority order. */
+        list_insert_ordered(&ready_list, &cur->elem, priority_more, NULL);
     }
+
   cur->status = THREAD_READY;
   schedule ();
   intr_set_level (old_level);
@@ -392,22 +401,66 @@ thread_foreach (thread_action_func *func, void *aux)
     }
 }
 
-/* Sets the current thread's priority to NEW_PRIORITY. */
-void
-thread_set_priority (int new_priority) 
+/* Function that compares the two threads associated with the provided
+   pointers to their 'elem' member. Returns true if the thread associated
+   with a_ has a higher priority than that of b_. */
+bool
+priority_more (const struct list_elem *a_, const struct list_elem *b_,
+               void *aux UNUSED)
 {
-  if (thread_mlfqs)
-    return;
-  thread_current ()->priority = new_priority;
+
+  struct thread *a = list_entry (a_, struct thread, elem);
+  struct thread *b = list_entry (b_, struct thread, elem);
+
+  return a->priority > b->priority;
+
 }
 
-/* Returns the current thread's priority. */
+/* Function that compares the two threads associated with the provided
+   pointers to their 'donor_elem' member. Returns true if the thread associated
+   with a_ has a lower priority than that of b_. */
+static bool
+donor_priority_less (const struct list_elem *a_, const struct list_elem *b_,
+               void *aux UNUSED)
+{
+  struct thread *a = list_entry (a_, struct thread, donor_elem);
+  struct thread *b = list_entry (b_, struct thread, donor_elem);
+
+  return a->priority < b->priority;
+}
+
+/* Sets the current thread's base priority to new_base_priority.
+   Updates the current thread's effective priority if necessary. */
+void
+thread_set_priority (int new_base_priority)
+{
+
+  if (thread_mlfqs)
+    return;
+
+  ASSERT (new_base_priority >= PRI_MIN);
+  ASSERT (new_base_priority <= PRI_MAX);
+
+  struct thread *t = thread_current ();
+
+  /* If the base priority is unchanged, do nothing. */
+  if (new_base_priority == t->base_priority)
+    return;
+
+  t->base_priority = new_base_priority;
+  thread_recalculate_priority ();
+
+  thread_yield ();
+}
+
+/* Returns the current thread's effective priority. */
 int
 thread_get_priority (void) 
 {
   return thread_current ()->priority;
 }
 
+
 /* Updates recent_cpu for a thread. */
 static void
 thread_update_recent_cpu (struct thread *t, void *aux UNUSED)
@@ -420,6 +473,31 @@ thread_update_recent_cpu (struct thread *t, void *aux UNUSED)
       = fp_add_int (fp_mul (recent_cpu_coeff, curr_recent_cpu), t->nice);
   // recent_cpu was updated, update priority.
   t->priority = calculate_bsd_priority (t->recent_cpu, t->nice);
+
+/* Recalculates the effective priority of the current thread. */
+void
+thread_recalculate_priority (void)
+{
+  struct thread *t = thread_current ();
+  
+  enum intr_level old_level = intr_disable ();
+  t->priority = t->base_priority;
+
+  /* If there are no donors to the current thread, then the effective
+     priority is just the base priority. */
+  if (!list_empty (&t->donors_list))
+    {
+      int max_donated_priority =
+        list_entry (list_max (&t->donors_list, donor_priority_less, NULL),
+                    struct thread, donor_elem)->priority;
+
+      /* The effective priority is the max donated priority if this is
+         higher than the base priority. */
+      if (max_donated_priority > t->priority)
+        t->priority = max_donated_priority;
+    }
+  intr_set_level (old_level);
+
 }
 
 /* Sets the current thread's nice value to NICE. */
@@ -458,6 +536,22 @@ thread_get_recent_cpu (void)
   return fp_round (fp_mul_int (thread_current ()->recent_cpu, 100));
 }
 
+/* Reinsert thread t into the ready list at its correct position
+   in descending order of priority. Used when this thread's priority
+   may have changed. Must be called with interrupts disabled. */
+void
+ready_list_reinsert (struct thread *t)
+{
+  ASSERT (intr_get_level () == INTR_OFF);
+
+  /* If the thread isn't ready to run, do nothing. */
+  if (t->status != THREAD_READY)
+    return;
+
+  list_remove (&t->elem);
+  list_insert_ordered (&ready_list, &t->elem, priority_more, NULL);
+}
+
 /* Idle thread.  Executes when no other thread is ready to run.
 
    The idle thread is initially put on the ready list by
@@ -544,11 +638,19 @@ init_thread (struct thread *t, const char *name, int nice, int priority,
   t->status = THREAD_BLOCKED;
   strlcpy (t->name, name, sizeof t->name);
   t->stack = (uint8_t *) t + PGSIZE;
+
   t->priority
       = thread_mlfqs ? calculate_bsd_priority (recent_cpu, nice) : priority;
   t->nice = nice;
   t->recent_cpu = recent_cpu;
+
+  t->base_priority = priority;
+
   t->magic = THREAD_MAGIC;
+  
+  list_init (&t->donors_list);
+  t->priority = t->base_priority;
+  t->waiting_lock = NULL;
 
   old_level = intr_disable ();
   list_push_back (&all_list, &t->allelem);