1 #include "cyclegraph.h"
7 /** Initializes a CycleGraph object. */
8 CycleGraph::CycleGraph() :
9 discovered(new HashTable<const CycleNode *, const CycleNode *, uintptr_t, 4, model_malloc, model_calloc, model_free>(16)),
15 /** CycleGraph destructor */
16 CycleGraph::~CycleGraph()
22 * Add a CycleNode to the graph, corresponding to a store ModelAction
23 * @param act The write action that should be added
24 * @param node The CycleNode that corresponds to the store
26 void CycleGraph::putNode(const ModelAction *act, CycleNode *node)
28 actionToNode.put(act, node);
29 #if SUPPORT_MOD_ORDER_DUMP
30 nodeList.push_back(node);
34 /** @return The corresponding CycleNode, if exists; otherwise NULL */
35 CycleNode * CycleGraph::getNode_noCreate(const ModelAction *act) const
37 return actionToNode.get(act);
40 /** @return The corresponding CycleNode, if exists; otherwise NULL */
41 CycleNode * CycleGraph::getNode_noCreate(const Promise *promise) const
43 return readerToPromiseNode.get(promise->get_action());
47 * @brief Returns the CycleNode corresponding to a given ModelAction
49 * Gets (or creates, if none exist) a CycleNode corresponding to a ModelAction
51 * @param action The ModelAction to find a node for
52 * @return The CycleNode paired with this action
54 CycleNode * CycleGraph::getNode(const ModelAction *action)
56 CycleNode *node = getNode_noCreate(action);
58 node = new CycleNode(action);
59 putNode(action, node);
65 * @brief Returns a CycleNode corresponding to a promise
67 * Gets (or creates, if none exist) a CycleNode corresponding to a promised
70 * @param promise The Promise generated by a reader
71 * @return The CycleNode corresponding to the Promise
73 CycleNode * CycleGraph::getNode(const Promise *promise)
75 const ModelAction *reader = promise->get_action();
76 CycleNode *node = getNode_noCreate(promise);
78 node = new CycleNode(promise);
79 readerToPromiseNode.put(reader, node);
85 * @return false if the resolution results in a cycle; true otherwise
87 bool CycleGraph::resolvePromise(ModelAction *reader, ModelAction *writer,
88 promise_list_t *mustResolve)
90 CycleNode *promise_node = readerToPromiseNode.get(reader);
91 CycleNode *w_node = actionToNode.get(writer);
95 return mergeNodes(w_node, promise_node, mustResolve);
96 /* No existing write-node; just convert the promise-node */
97 promise_node->resolvePromise(writer);
98 readerToPromiseNode.put(reader, NULL); /* erase promise_node */
99 putNode(writer, promise_node);
104 * @brief Merge two CycleNodes that represent the same write
106 * Note that this operation cannot be rolled back.
108 * @param w_node The write ModelAction node with which to merge
109 * @param p_node The Promise node to merge. Will be destroyed after this
111 * @param mustMerge Return (pass-by-reference) any additional Promises that
112 * must also be merged with w_node
114 * @return false if the merge results in a cycle; true otherwise
116 bool CycleGraph::mergeNodes(CycleNode *w_node, CycleNode *p_node,
117 promise_list_t *mustMerge)
119 ASSERT(!w_node->is_promise());
120 ASSERT(p_node->is_promise());
121 const Promise *promise = p_node->getPromise();
122 if (!promise->is_compatible(w_node->getAction())) {
127 /* Transfer back edges to w_node */
128 while (p_node->getNumBackEdges() > 0) {
129 CycleNode *back = p_node->removeBackEdge();
130 if (back != w_node) {
131 if (back->is_promise()) {
132 if (checkReachable(w_node, back)) {
133 /* Edge would create cycle; merge instead */
134 mustMerge->push_back(back->getPromise());
135 if (!mergeNodes(w_node, back, mustMerge))
138 back->addEdge(w_node);
140 addNodeEdge(back, w_node);
144 /* Transfer forward edges to w_node */
145 while (p_node->getNumEdges() > 0) {
146 CycleNode *forward = p_node->removeEdge();
147 if (forward != w_node) {
148 if (forward->is_promise()) {
149 if (checkReachable(forward, w_node)) {
150 mustMerge->push_back(forward->getPromise());
151 if (!mergeNodes(w_node, forward, mustMerge))
154 w_node->addEdge(forward);
156 addNodeEdge(w_node, forward);
161 readerToPromiseNode.put(promise->get_action(), NULL);
168 * Adds an edge between two CycleNodes.
169 * @param fromnode The edge comes from this CycleNode
170 * @param tonode The edge points to this CycleNode
171 * @return True, if new edge(s) are added; otherwise false
173 bool CycleGraph::addNodeEdge(CycleNode *fromnode, CycleNode *tonode)
178 hasCycles = checkReachable(tonode, fromnode);
180 if ((added = fromnode->addEdge(tonode)))
181 rollbackvector.push_back(fromnode);
184 * If the fromnode has a rmwnode that is not the tonode, we should add
185 * an edge between its rmwnode and the tonode
187 CycleNode *rmwnode = fromnode->getRMW();
188 if (rmwnode && rmwnode != tonode) {
190 hasCycles = checkReachable(tonode, rmwnode);
192 if (rmwnode->addEdge(tonode)) {
193 rollbackvector.push_back(rmwnode);
201 * @brief Add an edge between a write and the RMW which reads from it
203 * Handles special case of a RMW action, where the ModelAction rmw reads from
204 * the ModelAction from. The key differences are:
205 * (1) no write can occur in between the rmw and the from action.
206 * (2) Only one RMW action can read from a given write.
208 * @param from The edge comes from this ModelAction
209 * @param rmw The edge points to this ModelAction; this action must read from
212 void CycleGraph::addRMWEdge(const ModelAction *from, const ModelAction *rmw)
217 CycleNode *fromnode = getNode(from);
218 CycleNode *rmwnode = getNode(rmw);
220 /* Two RMW actions cannot read from the same write. */
221 if (fromnode->setRMW(rmwnode))
224 rmwrollbackvector.push_back(fromnode);
226 /* Transfer all outgoing edges from the from node to the rmw node */
227 /* This process should not add a cycle because either:
228 * (1) The rmw should not have any incoming edges yet if it is the
230 * (2) the fromnode is the new node and therefore it should not
231 * have any outgoing edges.
233 for (unsigned int i = 0; i < fromnode->getNumEdges(); i++) {
234 CycleNode *tonode = fromnode->getEdge(i);
235 if (tonode != rmwnode) {
236 if (rmwnode->addEdge(tonode))
237 rollbackvector.push_back(rmwnode);
241 addNodeEdge(fromnode, rmwnode);
244 #if SUPPORT_MOD_ORDER_DUMP
245 void CycleGraph::dumpNodes(FILE *file) const
247 for (unsigned int i = 0; i < nodeList.size(); i++) {
248 CycleNode *cn = nodeList[i];
249 const ModelAction *action = cn->getAction();
250 fprintf(file, "N%u [label=\"%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
251 if (cn->getRMW() != NULL) {
252 fprintf(file, "N%u -> N%u[style=dotted];\n", action->get_seq_number(), cn->getRMW()->getAction()->get_seq_number());
254 for (unsigned int j = 0; j < cn->getNumEdges(); j++) {
255 CycleNode *dst = cn->getEdge(j);
256 const ModelAction *dstaction = dst->getAction();
257 fprintf(file, "N%u -> N%u;\n", action->get_seq_number(), dstaction->get_seq_number());
262 void CycleGraph::dumpGraphToFile(const char *filename) const
265 sprintf(buffer, "%s.dot", filename);
266 FILE *file = fopen(buffer, "w");
267 fprintf(file, "digraph %s {\n", filename);
269 fprintf(file, "}\n");
275 * Checks whether one CycleNode can reach another.
276 * @param from The CycleNode from which to begin exploration
277 * @param to The CycleNode to reach
278 * @return True, @a from can reach @a to; otherwise, false
280 bool CycleGraph::checkReachable(const CycleNode *from, const CycleNode *to) const
282 std::vector< const CycleNode *, ModelAlloc<const CycleNode *> > queue;
285 queue.push_back(from);
286 discovered->put(from, from);
287 while (!queue.empty()) {
288 const CycleNode *node = queue.back();
293 for (unsigned int i = 0; i < node->getNumEdges(); i++) {
294 CycleNode *next = node->getEdge(i);
295 if (!discovered->contains(next)) {
296 discovered->put(next, next);
297 queue.push_back(next);
304 /** @return True, if the promise has failed; false otherwise */
305 bool CycleGraph::checkPromise(const ModelAction *fromact, Promise *promise) const
307 std::vector< CycleNode *, ModelAlloc<CycleNode *> > queue;
309 CycleNode *from = actionToNode.get(fromact);
311 queue.push_back(from);
312 discovered->put(from, from);
313 while (!queue.empty()) {
314 CycleNode *node = queue.back();
317 if (!node->is_promise() &&
318 promise->eliminate_thread(node->getAction()->get_tid()))
321 for (unsigned int i = 0; i < node->getNumEdges(); i++) {
322 CycleNode *next = node->getEdge(i);
323 if (!discovered->contains(next)) {
324 discovered->put(next, next);
325 queue.push_back(next);
332 void CycleGraph::startChanges()
334 ASSERT(rollbackvector.empty());
335 ASSERT(rmwrollbackvector.empty());
336 ASSERT(oldCycles == hasCycles);
339 /** Commit changes to the cyclegraph. */
340 void CycleGraph::commitChanges()
342 rollbackvector.clear();
343 rmwrollbackvector.clear();
344 oldCycles = hasCycles;
347 /** Rollback changes to the previous commit. */
348 void CycleGraph::rollbackChanges()
350 for (unsigned int i = 0; i < rollbackvector.size(); i++)
351 rollbackvector[i]->removeEdge();
353 for (unsigned int i = 0; i < rmwrollbackvector.size(); i++)
354 rmwrollbackvector[i]->clearRMW();
356 hasCycles = oldCycles;
357 rollbackvector.clear();
358 rmwrollbackvector.clear();
361 /** @returns whether a CycleGraph contains cycles. */
362 bool CycleGraph::checkForCycles() const
368 * @brief Constructor for a CycleNode
369 * @param act The ModelAction for this node
371 CycleNode::CycleNode(const ModelAction *act) :
379 * @brief Constructor for a Promise CycleNode
380 * @param promise The Promise which was generated
382 CycleNode::CycleNode(const Promise *promise) :
390 * @param i The index of the edge to return
391 * @returns The a CycleNode edge indexed by i
393 CycleNode * CycleNode::getEdge(unsigned int i) const
398 /** @returns The number of edges leaving this CycleNode */
399 unsigned int CycleNode::getNumEdges() const
404 CycleNode * CycleNode::getBackEdge(unsigned int i) const
406 return back_edges[i];
409 unsigned int CycleNode::getNumBackEdges() const
411 return back_edges.size();
415 * @brief Remove an element from a vector
416 * @param v The vector
417 * @param n The element to remove
418 * @return True if the element was found; false otherwise
420 template <typename T>
421 static bool vector_remove_node(std::vector<T, SnapshotAlloc<T> >& v, const T n)
423 for (unsigned int i = 0; i < v.size(); i++) {
425 v.erase(v.begin() + i);
433 * @brief Remove a (forward) edge from this CycleNode
434 * @return The CycleNode which was popped, if one exists; otherwise NULL
436 CycleNode * CycleNode::removeEdge()
441 CycleNode *ret = edges.back();
443 vector_remove_node(ret->back_edges, this);
448 * @brief Remove a (back) edge from this CycleNode
449 * @return The CycleNode which was popped, if one exists; otherwise NULL
451 CycleNode * CycleNode::removeBackEdge()
453 if (back_edges.empty())
456 CycleNode *ret = back_edges.back();
457 back_edges.pop_back();
458 vector_remove_node(ret->edges, this);
463 * Adds an edge from this CycleNode to another CycleNode.
464 * @param node The node to which we add a directed edge
465 * @return True if this edge is a new edge; false otherwise
467 bool CycleNode::addEdge(CycleNode *node)
469 for (unsigned int i = 0; i < edges.size(); i++)
470 if (edges[i] == node)
472 edges.push_back(node);
473 node->back_edges.push_back(this);
477 /** @returns the RMW CycleNode that reads from the current CycleNode */
478 CycleNode * CycleNode::getRMW() const
484 * Set a RMW action node that reads from the current CycleNode.
485 * @param node The RMW that reads from the current node
486 * @return True, if this node already was read by another RMW; false otherwise
487 * @see CycleGraph::addRMWEdge
489 bool CycleNode::setRMW(CycleNode *node)
498 * Convert a Promise CycleNode into a concrete-valued CycleNode. Should only be
499 * used when there's no existing ModelAction CycleNode for this write.
501 * @param writer The ModelAction which wrote the future value represented by
504 void CycleNode::resolvePromise(const ModelAction *writer)
506 ASSERT(is_promise());
507 ASSERT(promise->is_compatible(writer));
510 ASSERT(!is_promise());