model: wake up pending (sleep-set) actions for fences
authorBrian Norris <banorris@uci.edu>
Fri, 22 Feb 2013 07:07:55 +0000 (23:07 -0800)
committerBrian Norris <banorris@uci.edu>
Fri, 22 Feb 2013 07:08:34 +0000 (23:08 -0800)
This completes fence backtracking properly by waking up actions when the
appropriate fence interactions occur. This is a little more complicated
than the simple "could_synchronize()" test, since fence synchronization
can involve interaction of more than two actions.

So, pull the complexity of the "should we wake a thread up" computation
into its own function.

model.cc
model.h

index 8f0b3ce..998059e 100644 (file)
--- a/model.cc
+++ b/model.cc
@@ -313,14 +313,41 @@ void ModelChecker::execute_sleep_set()
        }
 }
 
        }
 }
 
+/**
+ * @brief Should the current action wake up a given thread?
+ *
+ * @param curr The current action
+ * @param thread The thread that we might wake up
+ * @return True, if we should wake up the sleeping thread; false otherwise
+ */
+bool ModelChecker::should_wake_up(const ModelAction *curr, const Thread *thread) const
+{
+       const ModelAction *asleep = thread->get_pending();
+       /* Don't allow partial RMW to wake anyone up */
+       if (curr->is_rmwr())
+               return false;
+       /* Synchronizing actions may have been backtracked */
+       if (asleep->could_synchronize_with(curr))
+               return true;
+       /* All acquire/release fences and fence-acquire/store-release */
+       if (asleep->is_fence() && asleep->is_acquire() && curr->is_release())
+               return true;
+       /* Fence-release + store can awake load-acquire on the same location */
+       if (asleep->is_read() && asleep->is_acquire() && curr->same_var(asleep) && curr->is_write()) {
+               ModelAction *fence_release = get_last_fence_release(curr->get_tid());
+               if (fence_release && *(get_last_action(thread->get_id())) < *fence_release)
+                       return true;
+       }
+       return false;
+}
+
 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
 {
        for (unsigned int i = 0; i < get_num_threads(); i++) {
                Thread *thr = get_thread(int_to_id(i));
                if (scheduler->is_sleep_set(thr)) {
 void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
 {
        for (unsigned int i = 0; i < get_num_threads(); i++) {
                Thread *thr = get_thread(int_to_id(i));
                if (scheduler->is_sleep_set(thr)) {
-                       ModelAction *pending_act = thr->get_pending();
-                       if ((!curr->is_rmwr()) && pending_act->could_synchronize_with(curr))
-                               //Remove this thread from sleep set
+                       if (should_wake_up(curr, thr))
+                               /* Remove this thread from sleep set */
                                scheduler->remove_sleep(thr);
                }
        }
                                scheduler->remove_sleep(thr);
                }
        }
diff --git a/model.h b/model.h
index de1fc63..bb548c2 100644 (file)
--- a/model.h
+++ b/model.h
@@ -149,6 +149,7 @@ private:
        void set_bad_synchronization();
        bool promises_expired() const;
        void execute_sleep_set();
        void set_bad_synchronization();
        bool promises_expired() const;
        void execute_sleep_set();
+       bool should_wake_up(const ModelAction *curr, const Thread *thread) const;
        void wake_up_sleeping_actions(ModelAction *curr);
        modelclock_t get_next_seq_num();
 
        void wake_up_sleeping_actions(ModelAction *curr);
        modelclock_t get_next_seq_num();