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[simgrid.git] / src / mc / checker / CommunicationDeterminismChecker.cpp
1 /* Copyright (c) 2008-2017. The SimGrid Team. All rights reserved.          */
2
3 /* This program is free software; you can redistribute it and/or modify it
4  * under the terms of the license (GNU LGPL) which comes with this package. */
5
6 #include <cstdint>
7
8 #include <xbt/dynar.h>
9 #include <xbt/dynar.hpp>
10 #include <xbt/log.h>
11 #include <xbt/sysdep.h>
12
13 #include "src/mc/Transition.hpp"
14 #include "src/mc/VisitedState.hpp"
15 #include "src/mc/checker/CommunicationDeterminismChecker.hpp"
16 #include "src/mc/mc_exit.hpp"
17 #include "src/mc/mc_private.hpp"
18 #include "src/mc/mc_record.hpp"
19 #include "src/mc/mc_request.hpp"
20 #include "src/mc/mc_smx.hpp"
21 #include "src/mc/mc_state.hpp"
22 #include "src/mc/remote/Client.hpp"
23
24 #include "smpi_request.hpp"
25
26 using simgrid::mc::remote;
27
28 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_comm_determinism, mc, "Logging specific to MC communication determinism detection");
29
30 /********** Global variables **********/
31
32 xbt_dynar_t initial_communications_pattern;
33 xbt_dynar_t incomplete_communications_pattern;
34
35 /********** Static functions ***********/
36
37 static e_mc_comm_pattern_difference_t compare_comm_pattern(simgrid::mc::PatternCommunication* comm1,
38                                                            simgrid::mc::PatternCommunication* comm2)
39 {
40   if(comm1->type != comm2->type)
41     return TYPE_DIFF;
42   if (comm1->rdv != comm2->rdv)
43     return RDV_DIFF;
44   if (comm1->src_proc != comm2->src_proc)
45     return SRC_PROC_DIFF;
46   if (comm1->dst_proc != comm2->dst_proc)
47     return DST_PROC_DIFF;
48   if (comm1->tag != comm2->tag)
49     return TAG_DIFF;
50   if (comm1->data.size() != comm2->data.size())
51     return DATA_SIZE_DIFF;
52   if (comm1->data != comm2->data)
53     return DATA_DIFF;
54   return NONE_DIFF;
55 }
56
57 static char* print_determinism_result(e_mc_comm_pattern_difference_t diff, int process,
58                                       simgrid::mc::PatternCommunication* comm, unsigned int cursor)
59 {
60   char* type;
61   char* res;
62
63   if (comm->type == simgrid::mc::PatternCommunicationType::send)
64     type = bprintf("The send communications pattern of the process %d is different!", process - 1);
65   else
66     type = bprintf("The recv communications pattern of the process %d is different!", process - 1);
67
68   switch(diff) {
69   case TYPE_DIFF:
70     res = bprintf("%s Different type for communication #%u", type, cursor);
71     break;
72   case RDV_DIFF:
73     res = bprintf("%s Different rdv for communication #%u", type, cursor);
74     break;
75   case TAG_DIFF:
76     res = bprintf("%s Different tag for communication #%u", type, cursor);
77     break;
78   case SRC_PROC_DIFF:
79     res = bprintf("%s Different source for communication #%u", type, cursor);
80     break;
81   case DST_PROC_DIFF:
82     res = bprintf("%s Different destination for communication #%u", type, cursor);
83     break;
84   case DATA_SIZE_DIFF:
85     res = bprintf("%s\n Different data size for communication #%u", type, cursor);
86     break;
87   case DATA_DIFF:
88     res = bprintf("%s\n Different data for communication #%u", type, cursor);
89     break;
90   default:
91     res = nullptr;
92     break;
93   }
94
95   return res;
96 }
97
98 static void update_comm_pattern(simgrid::mc::PatternCommunication* comm_pattern,
99                                 simgrid::mc::RemotePtr<simgrid::kernel::activity::CommImpl> comm_addr)
100 {
101   // HACK, type punning
102   simgrid::mc::Remote<simgrid::kernel::activity::CommImpl> temp_comm;
103   mc_model_checker->process().read(temp_comm, comm_addr);
104   simgrid::kernel::activity::CommImpl* comm = temp_comm.getBuffer();
105
106   smx_actor_t src_proc   = mc_model_checker->process().resolveActor(simgrid::mc::remote(comm->src_proc));
107   smx_actor_t dst_proc   = mc_model_checker->process().resolveActor(simgrid::mc::remote(comm->dst_proc));
108   comm_pattern->src_proc = src_proc->pid;
109   comm_pattern->dst_proc = dst_proc->pid;
110   comm_pattern->src_host = MC_smx_actor_get_host_name(src_proc);
111   comm_pattern->dst_host = MC_smx_actor_get_host_name(dst_proc);
112   if (comm_pattern->data.size() == 0 && comm->src_buff != nullptr) {
113     size_t buff_size;
114     mc_model_checker->process().read(&buff_size, remote(comm->dst_buff_size));
115     comm_pattern->data.resize(buff_size);
116     mc_model_checker->process().read_bytes(comm_pattern->data.data(), comm_pattern->data.size(),
117                                            remote(comm->src_buff));
118   }
119 }
120
121 namespace simgrid {
122 namespace mc {
123
124 void CommunicationDeterminismChecker::deterministic_comm_pattern(int process, simgrid::mc::PatternCommunication* comm,
125                                                                  int backtracking)
126 {
127   simgrid::mc::PatternCommunicationList* list =
128     xbt_dynar_get_as(initial_communications_pattern, process, simgrid::mc::PatternCommunicationList*);
129
130   if (not backtracking) {
131     e_mc_comm_pattern_difference_t diff = compare_comm_pattern(list->list[list->index_comm].get(), comm);
132
133     if (diff != NONE_DIFF) {
134       if (comm->type == simgrid::mc::PatternCommunicationType::send) {
135         this->send_deterministic = 0;
136         if (this->send_diff != nullptr)
137           xbt_free(this->send_diff);
138         this->send_diff = print_determinism_result(diff, process, comm, list->index_comm + 1);
139       } else {
140         this->recv_deterministic = 0;
141         if (this->recv_diff != nullptr)
142           xbt_free(this->recv_diff);
143         this->recv_diff = print_determinism_result(diff, process, comm, list->index_comm + 1);
144       }
145       if (_sg_mc_send_determinism && not this->send_deterministic) {
146         XBT_INFO("*********************************************************");
147         XBT_INFO("***** Non-send-deterministic communications pattern *****");
148         XBT_INFO("*********************************************************");
149         XBT_INFO("%s", this->send_diff);
150         xbt_free(this->send_diff);
151         this->send_diff = nullptr;
152         simgrid::mc::session->logState();
153         mc_model_checker->exit(SIMGRID_MC_EXIT_NON_DETERMINISM);
154       } else if (_sg_mc_comms_determinism && (not this->send_deterministic && not this->recv_deterministic)) {
155         XBT_INFO("****************************************************");
156         XBT_INFO("***** Non-deterministic communications pattern *****");
157         XBT_INFO("****************************************************");
158         XBT_INFO("%s", this->send_diff);
159         XBT_INFO("%s", this->recv_diff);
160         xbt_free(this->send_diff);
161         this->send_diff = nullptr;
162         xbt_free(this->recv_diff);
163         this->recv_diff = nullptr;
164         simgrid::mc::session->logState();
165         mc_model_checker->exit(SIMGRID_MC_EXIT_NON_DETERMINISM);
166       }
167     }
168   }
169 }
170
171 /********** Non Static functions ***********/
172
173 void CommunicationDeterminismChecker::get_comm_pattern(xbt_dynar_t list, smx_simcall_t request,
174                                                        e_mc_call_type_t call_type, int backtracking)
175 {
176   const smx_actor_t issuer = MC_smx_simcall_get_issuer(request);
177   simgrid::mc::PatternCommunicationList* initial_pattern =
178       xbt_dynar_get_as(initial_communications_pattern, issuer->pid, simgrid::mc::PatternCommunicationList*);
179   xbt_dynar_t incomplete_pattern = xbt_dynar_get_as(incomplete_communications_pattern, issuer->pid, xbt_dynar_t);
180
181   std::unique_ptr<simgrid::mc::PatternCommunication> pattern =
182       std::unique_ptr<simgrid::mc::PatternCommunication>(new simgrid::mc::PatternCommunication());
183   pattern->index = initial_pattern->index_comm + xbt_dynar_length(incomplete_pattern);
184
185   if (call_type == MC_CALL_TYPE_SEND) {
186     /* Create comm pattern */
187     pattern->type = simgrid::mc::PatternCommunicationType::send;
188     pattern->comm_addr = static_cast<simgrid::kernel::activity::CommImpl*>(simcall_comm_isend__getraw__result(request));
189
190     simgrid::mc::Remote<simgrid::kernel::activity::CommImpl> temp_synchro;
191     mc_model_checker->process().read(temp_synchro,
192                                      remote(static_cast<simgrid::kernel::activity::CommImpl*>(pattern->comm_addr)));
193     simgrid::kernel::activity::CommImpl* synchro =
194         static_cast<simgrid::kernel::activity::CommImpl*>(temp_synchro.getBuffer());
195
196     char* remote_name = mc_model_checker->process().read<char*>(
197         (std::uint64_t)(synchro->mbox ? &synchro->mbox->name_ : &synchro->mbox_cpy->name_));
198     pattern->rdv = mc_model_checker->process().read_string(remote_name);
199     pattern->src_proc = mc_model_checker->process().resolveActor(simgrid::mc::remote(synchro->src_proc))->pid;
200     pattern->src_host = MC_smx_actor_get_host_name(issuer);
201
202     simgrid::smpi::Request mpi_request =
203         mc_model_checker->process().read<simgrid::smpi::Request>((std::uint64_t)simcall_comm_isend__get__data(request));
204     pattern->tag = mpi_request.tag();
205
206     if (synchro->src_buff != nullptr) {
207       pattern->data.resize(synchro->src_buff_size);
208       mc_model_checker->process().read_bytes(pattern->data.data(), pattern->data.size(), remote(synchro->src_buff));
209     }
210     if(mpi_request.detached()){
211       if (not this->initial_communications_pattern_done) {
212         /* Store comm pattern */
213         simgrid::mc::PatternCommunicationList* list =
214             xbt_dynar_get_as(initial_communications_pattern, pattern->src_proc, simgrid::mc::PatternCommunicationList*);
215         list->list.push_back(std::move(pattern));
216       } else {
217         /* Evaluate comm determinism */
218         this->deterministic_comm_pattern(pattern->src_proc, pattern.get(), backtracking);
219         xbt_dynar_get_as(initial_communications_pattern, pattern->src_proc, simgrid::mc::PatternCommunicationList*)
220             ->index_comm++;
221       }
222       return;
223     }
224   } else if (call_type == MC_CALL_TYPE_RECV) {
225     pattern->type = simgrid::mc::PatternCommunicationType::receive;
226     pattern->comm_addr = static_cast<simgrid::kernel::activity::CommImpl*>(simcall_comm_irecv__getraw__result(request));
227
228     simgrid::smpi::Request mpi_request;
229     mc_model_checker->process().read(&mpi_request,
230                                      remote((simgrid::smpi::Request*)simcall_comm_irecv__get__data(request)));
231     pattern->tag = mpi_request.tag();
232
233     simgrid::mc::Remote<simgrid::kernel::activity::CommImpl> temp_comm;
234     mc_model_checker->process().read(temp_comm,
235                                      remote(static_cast<simgrid::kernel::activity::CommImpl*>(pattern->comm_addr)));
236     simgrid::kernel::activity::CommImpl* comm = temp_comm.getBuffer();
237
238     char* remote_name;
239     mc_model_checker->process().read(
240         &remote_name, remote(comm->mbox ? &simgrid::xbt::string::to_string_data(comm->mbox->name_).data
241                                         : &simgrid::xbt::string::to_string_data(comm->mbox_cpy->name_).data));
242     pattern->rdv = mc_model_checker->process().read_string(remote_name);
243     pattern->dst_proc = mc_model_checker->process().resolveActor(simgrid::mc::remote(comm->dst_proc))->pid;
244     pattern->dst_host = MC_smx_actor_get_host_name(issuer);
245   } else
246     xbt_die("Unexpected call_type %i", (int) call_type);
247
248   XBT_DEBUG("Insert incomplete comm pattern %p for process %lu", pattern.get(), issuer->pid);
249   xbt_dynar_t dynar = xbt_dynar_get_as(incomplete_communications_pattern, issuer->pid, xbt_dynar_t);
250   simgrid::mc::PatternCommunication* pattern2 = pattern.release();
251   xbt_dynar_push(dynar, &pattern2);
252 }
253
254 void CommunicationDeterminismChecker::complete_comm_pattern(
255     xbt_dynar_t list, simgrid::mc::RemotePtr<simgrid::kernel::activity::CommImpl> comm_addr, unsigned int issuer,
256     int backtracking)
257 {
258   simgrid::mc::PatternCommunication* current_comm_pattern;
259   unsigned int cursor = 0;
260   std::unique_ptr<simgrid::mc::PatternCommunication> comm_pattern;
261   int completed = 0;
262
263   /* Complete comm pattern */
264   xbt_dynar_foreach(xbt_dynar_get_as(incomplete_communications_pattern, issuer, xbt_dynar_t), cursor, current_comm_pattern)
265     if (remote(current_comm_pattern->comm_addr) == comm_addr) {
266       update_comm_pattern(current_comm_pattern, comm_addr);
267       completed = 1;
268       simgrid::mc::PatternCommunication* temp;
269       xbt_dynar_remove_at(xbt_dynar_get_as(incomplete_communications_pattern, issuer, xbt_dynar_t), cursor, &temp);
270       comm_pattern = std::unique_ptr<simgrid::mc::PatternCommunication>(temp);
271       XBT_DEBUG("Remove incomplete comm pattern for process %u at cursor %u", issuer, cursor);
272       break;
273     }
274
275   if (not completed)
276     xbt_die("Corresponding communication not found!");
277
278   simgrid::mc::PatternCommunicationList* pattern =
279       xbt_dynar_get_as(initial_communications_pattern, issuer, simgrid::mc::PatternCommunicationList*);
280
281   if (not this->initial_communications_pattern_done)
282     /* Store comm pattern */
283     pattern->list.push_back(std::move(comm_pattern));
284   else {
285     /* Evaluate comm determinism */
286     this->deterministic_comm_pattern(issuer, comm_pattern.get(), backtracking);
287     pattern->index_comm++;
288   }
289 }
290
291 CommunicationDeterminismChecker::CommunicationDeterminismChecker(Session& session) : Checker(session)
292 {
293 }
294
295 CommunicationDeterminismChecker::~CommunicationDeterminismChecker() = default;
296
297 RecordTrace CommunicationDeterminismChecker::getRecordTrace() // override
298 {
299   RecordTrace res;
300   for (auto const& state : stack_)
301     res.push_back(state->getTransition());
302   return res;
303 }
304
305 std::vector<std::string> CommunicationDeterminismChecker::getTextualTrace() // override
306 {
307   std::vector<std::string> trace;
308   for (auto const& state : stack_) {
309     smx_simcall_t req = &state->executed_req;
310     if (req)
311       trace.push_back(
312           simgrid::mc::request_to_string(req, state->transition.argument, simgrid::mc::RequestType::executed));
313   }
314   return trace;
315 }
316
317 void CommunicationDeterminismChecker::logState() // override
318 {
319   Checker::logState();
320   if (_sg_mc_comms_determinism && not this->recv_deterministic && this->send_deterministic) {
321     XBT_INFO("******************************************************");
322     XBT_INFO("**** Only-send-deterministic communication pattern ****");
323     XBT_INFO("******************************************************");
324     XBT_INFO("%s", this->recv_diff);
325   } else if (_sg_mc_comms_determinism && not this->send_deterministic && this->recv_deterministic) {
326     XBT_INFO("******************************************************");
327     XBT_INFO("**** Only-recv-deterministic communication pattern ****");
328     XBT_INFO("******************************************************");
329     XBT_INFO("%s", this->send_diff);
330   }
331   XBT_INFO("Expanded states = %lu", expandedStatesCount_);
332   XBT_INFO("Visited states = %lu", mc_model_checker->visited_states);
333   XBT_INFO("Executed transitions = %lu", mc_model_checker->executed_transitions);
334   XBT_INFO("Send-deterministic : %s", not this->send_deterministic ? "No" : "Yes");
335   if (_sg_mc_comms_determinism)
336     XBT_INFO("Recv-deterministic : %s", not this->recv_deterministic ? "No" : "Yes");
337 }
338
339 void CommunicationDeterminismChecker::prepare()
340 {
341   const int maxpid = MC_smx_get_maxpid();
342
343   // Create initial_communications_pattern elements:
344   initial_communications_pattern = simgrid::xbt::newDeleteDynar<simgrid::mc::PatternCommunicationList*>();
345   for (int i = 0; i < maxpid; i++) {
346     simgrid::mc::PatternCommunicationList* process_list_pattern = new simgrid::mc::PatternCommunicationList();
347     xbt_dynar_insert_at(initial_communications_pattern, i, &process_list_pattern);
348   }
349
350   // Create incomplete_communications_pattern elements:
351   incomplete_communications_pattern = xbt_dynar_new(sizeof(xbt_dynar_t), xbt_dynar_free_voidp);
352   for (int i = 0; i < maxpid; i++) {
353     xbt_dynar_t process_pattern = xbt_dynar_new(sizeof(simgrid::mc::PatternCommunication*), nullptr);
354     xbt_dynar_insert_at(incomplete_communications_pattern, i, &process_pattern);
355   }
356
357   std::unique_ptr<simgrid::mc::State> initial_state =
358       std::unique_ptr<simgrid::mc::State>(new simgrid::mc::State(++expandedStatesCount_));
359
360   XBT_DEBUG("********* Start communication determinism verification *********");
361
362   /* Get an enabled actor and insert it in the interleave set of the initial state */
363   for (auto& actor : mc_model_checker->process().actors())
364     if (simgrid::mc::actor_is_enabled(actor.copy.getBuffer()))
365       initial_state->addInterleavingSet(actor.copy.getBuffer());
366
367   stack_.push_back(std::move(initial_state));
368 }
369
370 static inline bool all_communications_are_finished()
371 {
372   for (size_t current_actor = 1; current_actor < MC_smx_get_maxpid(); current_actor++) {
373     xbt_dynar_t pattern = xbt_dynar_get_as(incomplete_communications_pattern, current_actor, xbt_dynar_t);
374     if (not xbt_dynar_is_empty(pattern)) {
375       XBT_DEBUG("Some communications are not finished, cannot stop the exploration! State not visited.");
376       return false;
377     }
378   }
379   return true;
380 }
381
382 void CommunicationDeterminismChecker::restoreState()
383 {
384   /* Intermediate backtracking */
385   simgrid::mc::State* state = stack_.back().get();
386   if (state->system_state) {
387     simgrid::mc::restore_snapshot(state->system_state);
388     MC_restore_communications_pattern(state);
389     return;
390   }
391
392   /* Restore the initial state */
393   simgrid::mc::session->restoreInitialState();
394
395   unsigned n = MC_smx_get_maxpid();
396   assert(n == xbt_dynar_length(incomplete_communications_pattern));
397   assert(n == xbt_dynar_length(initial_communications_pattern));
398   for (unsigned j=0; j < n ; j++) {
399     xbt_dynar_reset((xbt_dynar_t)xbt_dynar_get_as(incomplete_communications_pattern, j, xbt_dynar_t));
400     xbt_dynar_get_as(initial_communications_pattern, j, simgrid::mc::PatternCommunicationList*)->index_comm = 0;
401   }
402
403   /* Traverse the stack from the state at position start and re-execute the transitions */
404   for (std::unique_ptr<simgrid::mc::State> const& state : stack_) {
405     if (state == stack_.back())
406       break;
407
408     int req_num = state->transition.argument;
409     smx_simcall_t saved_req = &state->executed_req;
410     xbt_assert(saved_req);
411
412     /* because we got a copy of the executed request, we have to fetch the
413        real one, pointed by the request field of the issuer process */
414
415     const smx_actor_t issuer = MC_smx_simcall_get_issuer(saved_req);
416     smx_simcall_t req = &issuer->simcall;
417
418     /* TODO : handle test and testany simcalls */
419     e_mc_call_type_t call = MC_get_call_type(req);
420     mc_model_checker->handle_simcall(state->transition);
421     MC_handle_comm_pattern(call, req, req_num, nullptr, 1);
422     mc_model_checker->wait_for_requests();
423
424     /* Update statistics */
425     mc_model_checker->visited_states++;
426     mc_model_checker->executed_transitions++;
427   }
428 }
429
430 void CommunicationDeterminismChecker::main()
431 {
432   std::unique_ptr<simgrid::mc::VisitedState> visited_state = nullptr;
433   smx_simcall_t req = nullptr;
434
435   while (not stack_.empty()) {
436     /* Get current state */
437     simgrid::mc::State* state = stack_.back().get();
438
439     XBT_DEBUG("**************************************************");
440     XBT_DEBUG("Exploration depth = %zu (state = %d, interleaved processes = %zu)", stack_.size(), state->num,
441               state->interleaveSize());
442
443     /* Update statistics */
444     mc_model_checker->visited_states++;
445
446     if (stack_.size() <= (std::size_t)_sg_mc_max_depth)
447       req = MC_state_get_request(state);
448     else
449       req = nullptr;
450
451     if (req != nullptr && visited_state == nullptr) {
452
453       int req_num = state->transition.argument;
454
455       XBT_DEBUG("Execute: %s", simgrid::mc::request_to_string(req, req_num, simgrid::mc::RequestType::simix).c_str());
456
457       std::string req_str;
458       if (dot_output != nullptr)
459         req_str = simgrid::mc::request_get_dot_output(req, req_num);
460
461       mc_model_checker->executed_transitions++;
462
463       /* TODO : handle test and testany simcalls */
464       e_mc_call_type_t call = MC_CALL_TYPE_NONE;
465       if (_sg_mc_comms_determinism || _sg_mc_send_determinism)
466         call = MC_get_call_type(req);
467
468       /* Answer the request */
469       mc_model_checker->handle_simcall(state->transition);
470       /* After this call req is no longer useful */
471
472       if (not this->initial_communications_pattern_done)
473         MC_handle_comm_pattern(call, req, req_num, initial_communications_pattern, 0);
474       else
475         MC_handle_comm_pattern(call, req, req_num, nullptr, 0);
476
477       /* Wait for requests (schedules processes) */
478       mc_model_checker->wait_for_requests();
479
480       /* Create the new expanded state */
481       std::unique_ptr<simgrid::mc::State> next_state =
482           std::unique_ptr<simgrid::mc::State>(new simgrid::mc::State(++expandedStatesCount_));
483
484       /* If comm determinism verification, we cannot stop the exploration if some communications are not finished (at
485        * least, data are transferred). These communications  are incomplete and they cannot be analyzed and compared
486        * with the initial pattern. */
487       bool compare_snapshots = all_communications_are_finished() && this->initial_communications_pattern_done;
488
489       if (_sg_mc_max_visited_states != 0)
490         visited_state = visitedStates_.addVisitedState(expandedStatesCount_, next_state.get(), compare_snapshots);
491       else
492         visited_state = nullptr;
493
494       if (visited_state == nullptr) {
495
496         /* Get enabled actors and insert them in the interleave set of the next state */
497         for (auto& actor : mc_model_checker->process().actors())
498           if (simgrid::mc::actor_is_enabled(actor.copy.getBuffer()))
499             next_state->addInterleavingSet(actor.copy.getBuffer());
500
501         if (dot_output != nullptr)
502           fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n",
503             state->num,  next_state->num, req_str.c_str());
504
505       } else if (dot_output != nullptr)
506         fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", state->num,
507                 visited_state->original_num == -1 ? visited_state->num : visited_state->original_num, req_str.c_str());
508
509       stack_.push_back(std::move(next_state));
510
511     } else {
512
513       if (stack_.size() > (std::size_t) _sg_mc_max_depth)
514         XBT_WARN("/!\\ Max depth reached! /!\\ ");
515       else if (visited_state != nullptr)
516         XBT_DEBUG("State already visited (equal to state %d), exploration stopped on this path.",
517             visited_state->original_num == -1 ? visited_state->num : visited_state->original_num);
518       else
519         XBT_DEBUG("There are no more processes to interleave. (depth %zu)", stack_.size());
520
521       if (not this->initial_communications_pattern_done)
522         this->initial_communications_pattern_done = 1;
523
524       /* Trash the current state, no longer needed */
525       XBT_DEBUG("Delete state %d at depth %zu", state->num, stack_.size());
526       stack_.pop_back();
527
528       visited_state = nullptr;
529
530       /* Check for deadlocks */
531       if (mc_model_checker->checkDeadlock()) {
532         MC_show_deadlock();
533         throw simgrid::mc::DeadlockError();
534       }
535
536       while (not stack_.empty()) {
537         std::unique_ptr<simgrid::mc::State> state = std::move(stack_.back());
538         stack_.pop_back();
539         if (state->interleaveSize() && stack_.size() < (std::size_t)_sg_mc_max_depth) {
540           /* We found a back-tracking point, let's loop */
541           XBT_DEBUG("Back-tracking to state %d at depth %zu", state->num, stack_.size() + 1);
542           stack_.push_back(std::move(state));
543
544           this->restoreState();
545
546           XBT_DEBUG("Back-tracking to state %d at depth %zu done", stack_.back()->num, stack_.size());
547
548           break;
549         } else {
550           XBT_DEBUG("Delete state %d at depth %zu", state->num, stack_.size() + 1);
551         }
552       }
553     }
554   }
555
556   simgrid::mc::session->logState();
557 }
558
559 void CommunicationDeterminismChecker::run()
560 {
561   XBT_INFO("Check communication determinism");
562   simgrid::mc::session->initialize();
563
564   this->prepare();
565
566   this->main();
567 }
568
569 Checker* createCommunicationDeterminismChecker(Session& session)
570 {
571   return new CommunicationDeterminismChecker(session);
572 }
573
574 }
575 }