the initialized logic appears to be wrong... release/acquire pairs only

establish synchronization if the load reads the release store...  just because
all possible reads would synchronize doesn't mean that load can't fail to see them all...

diff --git a/model.cc b/model.cc
index 614b1a7..0bd9b61 100644 (file)
--- a/model.cc
+++ b/model.cc
@@ -365,15 +365,16 @@ void ModelChecker::build_reads_from_past(ModelAction *curr)
 
        ModelAction *last_seq_cst = NULL;
 
-       if (curr->is_seqcst())
-               last_seq_cst = get_last_seq_cst(curr->get_location());
-
        /* Track whether this object has been initialized */
        bool initialized = false;
-       /* Would each action synchronize if we read from it? */
-       bool all_synch = true;
-       /* Is the may_read_from set empty? (tracked locally) */
-       bool empty = true;
+
+       if (curr->is_seqcst()) {
+               last_seq_cst = get_last_seq_cst(curr->get_location());
+               /* We have to at least see the last sequentially consistent write,
+                        so we are initialized. */
+               if (last_seq_cst != NULL)
+                       initialized = true;
+       }
 
        /* Iterate over all threads */
        for (i = 0; i < thrd_lists->size(); i++) {
@@ -395,11 +396,6 @@ void ModelChecker::build_reads_from_past(ModelAction *curr)
                                        curr->print();
                                }
                                curr->get_node()->add_read_from(act);
-                               empty = false;
-
-                               if (!(act->is_release() && curr->is_acquire())
-                                               && !act->same_thread(curr))
-                                       all_synch = false;
                        }
 
                        /* Include at most one act per-thread that "happens before" curr */
@@ -410,14 +406,11 @@ void ModelChecker::build_reads_from_past(ModelAction *curr)
                }
        }
 
-       if (!empty && all_synch)
-               initialized = true;
-
        if (!initialized) {
                /* TODO: need a more informative way of reporting errors */
                printf("ERROR: may read from uninitialized atomic\n");
        }
-
+       
        if (DBG_ENABLED() || !initialized) {
                printf("Reached read action:\n");
                curr->print();
@@ -425,7 +418,7 @@ void ModelChecker::build_reads_from_past(ModelAction *curr)
                curr->get_node()->print_may_read_from();
                printf("End printing may_read_from\n");
        }
-
+       
        ASSERT(initialized);
 }