X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=model.cc;h=c86a6f676718d3fab6122282483786dd85589cb0;hb=a02d0bed3bc5ab757c3ed30a9589c53b05919688;hp=85e1f849cc7a42f7c10139321b360414b818b102;hpb=471e92c4bc5de8629d044a61eea5e1ff0670daad;p=model-checker.git

diff --git a/model.cc b/model.cc
index 85e1f84..c86a6f6 100644
--- a/model.cc
+++ b/model.cc
@@ -7,6 +7,7 @@
 #include "snapshot-interface.h"
 #include "common.h"
 #include "clockvector.h"
+#include "cyclegraph.h"
 
 #define INITIAL_THREAD_ID	0
 
@@ -31,7 +32,8 @@ ModelChecker::ModelChecker()
 	obj_thrd_map(new std::map<void *, std::vector<action_list_t> >()),
 	thrd_last_action(new std::vector<ModelAction *>(1)),
 	node_stack(new NodeStack()),
-	next_backtrack(NULL)
+	next_backtrack(NULL),
+	cyclegraph(new CycleGraph())
 {
 }
 
@@ -49,6 +51,7 @@ ModelChecker::~ModelChecker()
 	delete thrd_last_action;
 	delete node_stack;
 	delete scheduler;
+	delete cyclegraph;
 }
 
 /**
@@ -126,11 +129,19 @@ thread_id_t ModelChecker::get_next_replay_thread()
 	next = node_stack->get_next()->get_action();
 
 	if (next == diverge) {
-		Node *node = next->get_node()->get_parent();
-
+		Node *nextnode = next->get_node();
 		/* Reached divergence point */
+		if (nextnode->increment_read_from()) {
+			/* The next node will read from a different value */
+			tid = next->get_tid();
+			node_stack->pop_restofstack(2);
+		} else {
+			/* Make a different thread execute for next step */
+			Node *node = nextnode->get_parent();
+			tid = node->get_next_backtrack();
+			node_stack->pop_restofstack(1);
+		}
 		DEBUG("*** Divergence point ***\n");
-		tid = node->get_next_backtrack();
 		diverge = NULL;
 	} else {
 		tid = next->get_tid();
@@ -151,7 +162,10 @@ bool ModelChecker::next_execution()
 	DBG();
 
 	num_executions++;
-	print_summary();
+
+	if (isfeasible() || DBG_ENABLED())
+		print_summary();
+
 	if ((diverge = model->get_next_backtrack()) == NULL)
 		return false;
 
@@ -177,8 +191,9 @@ ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 			return NULL;
 	}
 	/* linear search: from most recent to oldest */
+	action_list_t *list = &(*obj_map)[act->get_location()];
 	action_list_t::reverse_iterator rit;
-	for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
+	for (rit = list->rbegin(); rit != list->rend(); rit++) {
 		ModelAction *prev = *rit;
 		if (act->is_synchronizing(prev))
 			return prev;
@@ -220,6 +235,11 @@ void ModelChecker::set_backtracking(ModelAction *act)
 	}
 }
 
+/**
+ * Returns last backtracking point. The model checker will explore a different
+ * path for this point in the next execution.
+ * @return The ModelAction at which the next execution should diverge.
+ */
 ModelAction * ModelChecker::get_next_backtrack()
 {
 	ModelAction *next = next_backtrack;
@@ -229,8 +249,6 @@ ModelAction * ModelChecker::get_next_backtrack()
 
 void ModelChecker::check_current_action(void)
 {
-	Node *currnode;
-
 	ModelAction *curr = this->current_action;
 	ModelAction *tmp;
 	current_action = NULL;
@@ -239,6 +257,15 @@ void ModelChecker::check_current_action(void)
 		return;
 	}
 
+	if (curr->is_rmw()) {
+		//We have a RMW action
+		process_rmw(curr);
+		//Force the current thread to continue since the RMW should be atomic
+		nextThread = thread_current()->get_id();
+		delete curr;
+		return;
+	}
+
 	tmp = node_stack->explore_action(curr);
 	if (tmp) {
 		/* Discard duplicate ModelAction; use action from NodeStack */
@@ -261,30 +288,121 @@ void ModelChecker::check_current_action(void)
 		th->set_creation(curr);
 	}
 
+	/* Is there a better interface for setting the next thread rather
+		 than this field/convoluted approach?  Perhaps like just returning
+		 it or something? */
+
 	nextThread = get_next_replay_thread();
 
-	currnode = curr->get_node()->get_parent();
+	Node *currnode = curr->get_node();
+	Node *parnode = currnode->get_parent();
 
-	if (!currnode->backtrack_empty())
+	if (!parnode->backtrack_empty()||!currnode->readsfrom_empty())
 		if (!next_backtrack || *curr > *next_backtrack)
 			next_backtrack = curr;
 
 	set_backtracking(curr);
 
-	add_action_to_lists(curr);
-
 	/* Assign reads_from values */
-	/* TODO: perform release/acquire synchronization here; include
-	 * reads_from as ModelAction member? */
 	Thread *th = get_thread(curr->get_tid());
-	int value = VALUE_NONE;
+	uint64_t value = VALUE_NONE;
 	if (curr->is_read()) {
-		const ModelAction *reads_from = curr->get_node()->get_next_read_from();
+		const ModelAction *reads_from = curr->get_node()->get_read_from();
 		value = reads_from->get_value();
 		/* Assign reads_from, perform release/acquire synchronization */
 		curr->read_from(reads_from);
+		r_modification_order(curr,reads_from);
+	} else if (curr->is_write()) {
+		w_modification_order(curr);
 	}
+
 	th->set_return_value(value);
+
+	/* Add action to list last.  */
+	add_action_to_lists(curr);
+}
+
+/** @returns whether the current trace is feasible. */
+bool ModelChecker::isfeasible() {
+	return !cyclegraph->checkForCycles();
+}
+
+/** Process a RMW by converting previous read into a RMW. */
+void ModelChecker::process_rmw(ModelAction * act) {
+	int tid = id_to_int(act->get_tid());
+	ModelAction *lastread=get_last_action(tid);
+	lastread->upgrade_rmw(act);
+	cyclegraph->addRMWEdge(lastread->get_reads_from(),lastread);
+}
+
+/**
+ * Updates the cyclegraph with the constraints imposed from the current read.
+ * @param curr The current action. Must be a read.
+ * @param rf The action that curr reads from. Must be a write.
+ */
+void ModelChecker::r_modification_order(ModelAction * curr, const ModelAction *rf) {
+	std::vector<action_list_t> *thrd_lists = &(*obj_thrd_map)[curr->get_location()];
+	unsigned int i;
+	ASSERT(curr->is_read());
+
+	/* Iterate over all threads */
+	for (i = 0; i < thrd_lists->size(); i++) {
+		/* Iterate over actions in thread, starting from most recent */
+		action_list_t *list = &(*thrd_lists)[i];
+		action_list_t::reverse_iterator rit;
+		for (rit = list->rbegin(); rit != list->rend(); rit++) {
+			ModelAction *act = *rit;
+
+			/* Include at most one act per-thread that "happens before" curr */
+			if (act->happens_before(curr)) {
+				if (act->is_read()) {
+					const ModelAction * prevreadfrom=act->get_reads_from();
+					if (rf!=prevreadfrom)
+						cyclegraph->addEdge(rf, prevreadfrom);
+				} else if (rf!=act) {
+					cyclegraph->addEdge(rf, act);
+				}
+				break;
+			}
+		}
+	}
+}
+
+/**
+ * Updates the cyclegraph with the constraints imposed from the current write.
+ * @param curr The current action. Must be a write.
+ */
+void ModelChecker::w_modification_order(ModelAction * curr) {
+	std::vector<action_list_t> *thrd_lists = &(*obj_thrd_map)[curr->get_location()];
+	unsigned int i;
+	ASSERT(curr->is_write());
+
+	if (curr->is_seqcst()) {
+		/* We have to at least see the last sequentially consistent write,
+			 so we are initialized. */
+		ModelAction * last_seq_cst=get_last_seq_cst(curr->get_location());
+		if (last_seq_cst!=NULL)
+			cyclegraph->addEdge(curr, last_seq_cst);
+	}
+
+	/* Iterate over all threads */
+	for (i = 0; i < thrd_lists->size(); i++) {
+		/* Iterate over actions in thread, starting from most recent */
+		action_list_t *list = &(*thrd_lists)[i];
+		action_list_t::reverse_iterator rit;
+		for (rit = list->rbegin(); rit != list->rend(); rit++) {
+			ModelAction *act = *rit;
+
+			/* Include at most one act per-thread that "happens before" curr */
+			if (act->happens_before(curr)) {
+				if (act->is_read()) {
+					cyclegraph->addEdge(curr, act->get_reads_from());
+				} else
+					cyclegraph->addEdge(curr, act);
+				break;
+			}
+		}
+	}
 }
 
 /**
@@ -319,6 +437,23 @@ ModelAction * ModelChecker::get_last_action(thread_id_t tid)
 	return (*thrd_last_action)[id_to_int(tid)];
 }
 
+/**
+ * Gets the last memory_order_seq_cst action (in the total global sequence)
+ * performed on a particular object (i.e., memory location).
+ * @param location The object location to check
+ * @return The last seq_cst action performed
+ */
+ModelAction * ModelChecker::get_last_seq_cst(const void *location)
+{
+	action_list_t *list = &(*obj_map)[location];
+	/* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
+	action_list_t::reverse_iterator rit;
+	for (rit = list->rbegin(); rit != list->rend(); rit++)
+		if ((*rit)->is_write() && (*rit)->is_seqcst())
+			return *rit;
+	return NULL;
+}
+
 ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
 {
 	ModelAction *parent = get_last_action(tid);
@@ -327,6 +462,11 @@ ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
 	return parent;
 }
 
+/**
+ * Returns the clock vector for a given thread.
+ * @param tid The thread whose clock vector we want
+ * @return Desired clock vector
+ */
 ClockVector * ModelChecker::get_cv(thread_id_t tid) {
 	return get_parent_action(tid)->get_cv();
 }
@@ -342,13 +482,24 @@ void ModelChecker::build_reads_from_past(ModelAction *curr)
 {
 	std::vector<action_list_t> *thrd_lists = &(*obj_thrd_map)[curr->get_location()];
 	unsigned int i;
-
 	ASSERT(curr->is_read());
 
+	ModelAction *last_seq_cst = NULL;
+
 	/* Track whether this object has been initialized */
 	bool initialized = false;
 
+	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++) {
+		/* Iterate over actions in thread, starting from most recent */
 		action_list_t *list = &(*thrd_lists)[i];
 		action_list_t::reverse_iterator rit;
 		for (rit = list->rbegin(); rit != list->rend(); rit++) {
@@ -358,12 +509,15 @@ void ModelChecker::build_reads_from_past(ModelAction *curr)
 			if (!act->is_write())
 				continue;
 
-			DEBUG("Adding action to may_read_from:\n");
-			if (DBG_ENABLED()) {
-				act->print();
-				curr->print();
+			/* Don't consider more than one seq_cst write if we are a seq_cst read. */
+			if (!act->is_seqcst() || !curr->is_seqcst() || act == last_seq_cst) {
+				DEBUG("Adding action to may_read_from:\n");
+				if (DBG_ENABLED()) {
+					act->print();
+					curr->print();
+				}
+				curr->get_node()->add_read_from(act);
 			}
-			curr->get_node()->add_read_from(act);
 
 			/* Include at most one act per-thread that "happens before" curr */
 			if (act->happens_before(curr)) {
@@ -377,7 +531,7 @@ void ModelChecker::build_reads_from_past(ModelAction *curr)
 		/* 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();
@@ -385,7 +539,7 @@ void ModelChecker::build_reads_from_past(ModelAction *curr)
 		curr->get_node()->print_may_read_from();
 		printf("End printing may_read_from\n");
 	}
-
+	
 	ASSERT(initialized);
 }
 
@@ -410,6 +564,8 @@ void ModelChecker::print_summary(void)
 
 	scheduler->print();
 
+	if (!isfeasible())
+		printf("INFEASIBLE EXECUTION!\n");
 	print_list(action_trace);
 	printf("\n");
 }
@@ -426,6 +582,17 @@ void ModelChecker::remove_thread(Thread *t)
 	scheduler->remove_thread(t);
 }
 
+/**
+ * Switch from a user-context to the "master thread" context (a.k.a. system
+ * context). This switch is made with the intention of exploring a particular
+ * model-checking action (described by a ModelAction object). Must be called
+ * from a user-thread context.
+ * @param act The current action that will be explored. May be NULL, although
+ * there is little reason to switch to the model-checker without an action to
+ * explore (note: act == NULL is sometimes used as a hack to allow a thread to
+ * yield control without performing any progress; see thrd_join()).
+ * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
+ */
 int ModelChecker::switch_to_master(ModelAction *act)
 {
 	Thread *old;