model: refactor "get next thread" code

get_next_replay_thread() might as well handle all the Thread decisions for the
model-checker. Refactor, and rename to get_next_thread().

diff --git a/model.cc b/model.cc
index c8af6cc4f5bfb2d2c878e6aa035e2cf712d56e29..90c7ad91493bf50bd0c7859ba1d01db7d12afb09 100644 (file)
--- a/model.cc
+++ b/model.cc
@@ -98,16 +98,29 @@ modelclock_t ModelChecker::get_next_seq_num()
 }
 
 /**
- * Choose the next thread in the replay sequence.
+ * @brief Choose the next thread to execute.
  *
- * If the replay sequence has reached the 'diverge' point, returns a thread
- * from the backtracking set. Otherwise, simply returns the next thread in the
- * sequence that is being replayed.
+ * This function chooses the next thread that should execute. It can force the
+ * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
+ * followed by a THREAD_START, or it can enforce execution replay/backtracking.
+ * The model-checker may have no preference regarding the next thread (i.e.,
+ * when exploring a new execution ordering), in which case this will return
+ * NULL.
+ * @param curr The current ModelAction. This action might guide the choice of
+ * next thread.
+ * @return The next thread to run. If the model-checker has no preference, NULL.
  */
-Thread * ModelChecker::get_next_replay_thread()
+Thread * ModelChecker::get_next_thread(ModelAction *curr)
 {
        thread_id_t tid;
 
+       /* Do not split atomic actions. */
+       if (curr->is_rmwr())
+               return thread_current();
+       /* The THREAD_CREATE action points to the created Thread */
+       else if (curr->get_type() == THREAD_CREATE)
+               return (Thread *)curr->get_location();
+
        /* Have we completed exploring the preselected path? */
        if (diverge == NULL)
                return NULL;
@@ -362,14 +375,7 @@ Thread * ModelChecker::check_current_action(ModelAction *curr)
 
        set_backtracking(curr);
 
-       /* Do not split atomic actions. */
-       if (curr->is_rmwr())
-               return thread_current();
-       /* The THREAD_CREATE action points to the created Thread */
-       else if (curr->get_type() == THREAD_CREATE)
-               return (Thread *)curr->get_location();
-       else
-               return get_next_replay_thread();
+       return get_next_thread(curr);
 }
 
 /** @returns whether the current partial trace must be a prefix of a

diff --git a/model.h b/model.h
index b2f7897a310f7dc66fa88ce970893c43c252059c..1b6bb10a285e4046e4b9bbe727526abf1849f071 100644 (file)
--- a/model.h
+++ b/model.h
@@ -105,7 +105,7 @@ private:
 
        ModelAction * get_last_conflict(ModelAction *act);
        void set_backtracking(ModelAction *act);
-       Thread * get_next_replay_thread();
+       Thread * get_next_thread(ModelAction *curr);
        ModelAction * get_next_backtrack();
        void reset_to_initial_state();
        bool resolve_promises(ModelAction *curr);