1 /* Copyright (c) 2016-2022. The SimGrid Team. All rights reserved. */
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. */
6 #include "src/mc/Session.hpp"
7 #include "src/mc/Transition.hpp"
8 #include "src/mc/VisitedState.hpp"
9 #include "src/mc/checker/SafetyChecker.hpp"
10 #include "src/mc/mc_config.hpp"
11 #include "src/mc/mc_exit.hpp"
12 #include "src/mc/mc_private.hpp"
13 #include "src/mc/mc_record.hpp"
15 #include "src/xbt/mmalloc/mmprivate.h"
17 #include "xbt/sysdep.h"
26 using api = simgrid::mc::Api;
28 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_safety, mc, "Logging specific to MC safety verification ");
33 void SafetyChecker::check_non_termination(const State* current_state)
35 for (auto state = stack_.rbegin(); state != stack_.rend(); ++state)
36 if (api::get().snapshot_equal((*state)->system_state_.get(), current_state->system_state_.get())) {
37 XBT_INFO("Non-progressive cycle: state %d -> state %d", (*state)->num_, current_state->num_);
38 XBT_INFO("******************************************");
39 XBT_INFO("*** NON-PROGRESSIVE CYCLE DETECTED ***");
40 XBT_INFO("******************************************");
41 XBT_INFO("Counter-example execution trace:");
42 for (auto const& s : get_textual_trace())
43 XBT_INFO(" %s", s.c_str());
44 api::get().dump_record_path();
45 api::get().log_state();
47 throw TerminationError();
51 RecordTrace SafetyChecker::get_record_trace() // override
54 for (auto const& state : stack_)
55 res.push_back(state->get_transition());
59 std::vector<std::string> SafetyChecker::get_textual_trace() // override
61 std::vector<std::string> trace;
62 for (auto const& state : stack_)
63 trace.push_back(state->transition_.textual);
67 void SafetyChecker::log_state() // override
69 XBT_INFO("Expanded states = %lu", expanded_states_count_);
70 XBT_INFO("Visited states = %lu", api::get().mc_get_visited_states());
71 XBT_INFO("Executed transitions = %lu", api::get().mc_get_executed_trans());
74 void SafetyChecker::run()
76 /* This function runs the DFS algorithm the state space.
77 * We do so iteratively instead of recursively, dealing with the call stack manually.
78 * This allows one to explore the call stack at will. */
80 while (not stack_.empty()) {
81 /* Get current state */
82 State* state = stack_.back().get();
84 XBT_DEBUG("**************************************************");
85 XBT_VERB("Exploration depth=%zu (state=%p, num %d)(%zu interleave)", stack_.size(), state, state->num_,
88 api::get().mc_inc_visited_states();
90 // Backtrack if we reached the maximum depth
91 if (stack_.size() > (std::size_t)_sg_mc_max_depth) {
92 if (reductionMode_ == ReductionMode::dpor) {
93 XBT_ERROR("/!\\ Max depth of %d reached! THIS WILL PROBABLY BREAK the dpor reduction /!\\",
94 _sg_mc_max_depth.get());
95 XBT_ERROR("/!\\ If bad things happen, disable dpor with --cfg=model-check/reduction:none /!\\");
97 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
102 // Backtrack if we are revisiting a state we saw previously
103 if (visited_state_ != nullptr) {
104 XBT_DEBUG("State already visited (equal to state %d), exploration stopped on this path.",
105 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num);
107 visited_state_ = nullptr;
112 // Search an enabled transition in the current state; backtrack if the interleave set is empty
113 // get_request also sets state.transition to be the one corresponding to the returned req
114 smx_simcall_t req = api::get().mc_state_choose_request(state);
115 // req is now the transition of the process that was selected to be executed
117 if (req == nullptr) {
118 XBT_DEBUG("There remains %zu actors, but none to interleave (depth %zu).",
119 mc_model_checker->get_remote_process().actors().size(), stack_.size() + 1);
121 if (mc_model_checker->get_remote_process().actors().empty())
122 mc_model_checker->finalize_app();
127 // If there are processes to interleave and the maximum depth has not been
128 // reached then perform one step of the exploration algorithm.
129 XBT_DEBUG("Execute: %s", api::get().request_to_string(req, state->transition_.times_considered_).c_str());
132 if (dot_output != nullptr)
133 req_str = api::get().request_get_dot_output(req, state->transition_.times_considered_);
135 api::get().mc_inc_executed_trans();
137 /* Actually answer the request: let execute the selected request (MCed does one step) */
138 RemotePtr<simgrid::kernel::actor::SimcallObserver> remote_observer =
139 api::get().execute(state->transition_, &state->executed_req_);
141 /* Create the new expanded state (copy the state of MCed into our MCer data) */
142 ++expanded_states_count_;
143 auto next_state = std::make_unique<State>(expanded_states_count_);
144 next_state->remote_observer_ = remote_observer;
146 if (_sg_mc_termination)
147 this->check_non_termination(next_state.get());
149 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
150 if (_sg_mc_max_visited_states > 0)
151 visited_state_ = visited_states_.addVisitedState(expanded_states_count_, next_state.get(), true);
153 /* If this is a new state (or if we don't care about state-equality reduction) */
154 if (visited_state_ == nullptr) {
155 /* Get an enabled process and insert it in the interleave set of the next state */
156 auto actors = api::get().get_actors();
157 for (auto& remoteActor : actors) {
158 auto actor = remoteActor.copy.get_buffer();
159 if (get_session().actor_is_enabled(actor->get_pid())) {
160 next_state->mark_todo(actor);
161 if (reductionMode_ == ReductionMode::dpor)
162 break; // With DPOR, we take the first enabled transition
166 if (dot_output != nullptr)
167 std::fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", state->num_, next_state->num_, req_str.c_str());
169 } else if (dot_output != nullptr)
170 std::fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", state->num_,
171 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num,
174 stack_.push_back(std::move(next_state));
177 XBT_INFO("No property violation found.");
178 api::get().log_state();
181 void SafetyChecker::backtrack()
185 api::get().mc_check_deadlock();
187 /* Traverse the stack backwards until a state with a non empty interleave set is found, deleting all the states that
188 * have it empty in the way. For each deleted state, check if the request that has generated it (from its
189 * predecessor state), depends on any other previous request executed before it. If it does then add it to the
190 * interleave set of the state that executed that previous request. */
192 while (not stack_.empty()) {
193 std::unique_ptr<State> state = std::move(stack_.back());
195 if (reductionMode_ == ReductionMode::dpor) {
196 kernel::actor::ActorImpl* issuer = api::get().simcall_get_issuer(&state->executed_req_);
197 for (auto i = stack_.rbegin(); i != stack_.rend(); ++i) {
198 State* prev_state = i->get();
199 if (state->executed_req_.issuer_ == prev_state->executed_req_.issuer_) {
200 XBT_DEBUG("Simcall %s and %s with same issuer", SIMIX_simcall_name(state->executed_req_),
201 SIMIX_simcall_name(prev_state->executed_req_));
203 } else if (api::get().requests_are_dependent(state->remote_observer_, state->remote_observer_)) {
204 if (XBT_LOG_ISENABLED(mc_safety, xbt_log_priority_debug)) {
205 XBT_DEBUG("Dependent Transitions:");
206 int value = prev_state->transition_.times_considered_;
207 smx_simcall_t prev_req = &prev_state->executed_req_;
208 XBT_DEBUG("%s (state=%d)", api::get().request_to_string(prev_req, value).c_str(), prev_state->num_);
209 value = state->transition_.times_considered_;
210 prev_req = &state->executed_req_;
211 XBT_DEBUG("%s (state=%d)", api::get().request_to_string(prev_req, value).c_str(), state->num_);
214 if (not prev_state->actor_states_[issuer->get_pid()].is_done())
215 prev_state->mark_todo(issuer);
217 XBT_DEBUG("Actor %s %ld is in done set", api::get().get_actor_name(issuer).c_str(), issuer->get_pid());
220 const kernel::actor::ActorImpl* previous_issuer = api::get().simcall_get_issuer(&prev_state->executed_req_);
221 XBT_DEBUG("Simcall %s, process %ld (state %d) and simcall %s, process %ld (state %d) are independent",
222 SIMIX_simcall_name(state->executed_req_), issuer->get_pid(), state->num_,
223 SIMIX_simcall_name(prev_state->executed_req_), previous_issuer->get_pid(), prev_state->num_);
228 if (state->count_todo() && stack_.size() < (std::size_t)_sg_mc_max_depth) {
229 /* We found a back-tracking point, let's loop */
230 XBT_DEBUG("Back-tracking to state %d at depth %zu", state->num_, stack_.size() + 1);
231 stack_.push_back(std::move(state));
232 this->restore_state();
233 XBT_DEBUG("Back-tracking to state %d at depth %zu done", stack_.back()->num_, stack_.size());
236 XBT_DEBUG("Delete state %d at depth %zu", state->num_, stack_.size() + 1);
241 void SafetyChecker::restore_state()
243 /* Intermediate backtracking */
244 const State* last_state = stack_.back().get();
245 if (last_state->system_state_) {
246 api::get().restore_state(last_state->system_state_);
250 get_session().restore_initial_state();
252 /* Traverse the stack from the state at position start and re-execute the transitions */
253 for (std::unique_ptr<State> const& state : stack_) {
254 if (state == stack_.back())
256 api::get().execute(state->transition_, &state->executed_req_);
257 /* Update statistics */
258 api::get().mc_inc_visited_states();
259 api::get().mc_inc_executed_trans();
263 SafetyChecker::SafetyChecker(Session* session) : Checker(session)
265 reductionMode_ = reduction_mode;
266 if (_sg_mc_termination)
267 reductionMode_ = ReductionMode::none;
268 else if (reductionMode_ == ReductionMode::unset)
269 reductionMode_ = ReductionMode::dpor;
271 if (_sg_mc_termination)
272 XBT_INFO("Check non progressive cycles");
274 XBT_INFO("Check a safety property. Reduction is: %s.",
275 (reductionMode_ == ReductionMode::none ? "none"
276 : (reductionMode_ == ReductionMode::dpor ? "dpor" : "unknown")));
278 get_session().take_initial_snapshot();
280 XBT_DEBUG("Starting the safety algorithm");
282 ++expanded_states_count_;
283 auto initial_state = std::make_unique<State>(expanded_states_count_);
285 XBT_DEBUG("**************************************************");
287 /* Get an enabled actor and insert it in the interleave set of the initial state */
288 auto actors = api::get().get_actors();
289 XBT_DEBUG("Initial state. %zu actors to consider", actors.size());
290 for (auto& actor : actors)
291 if (get_session().actor_is_enabled(actor.copy.get_buffer()->get_pid())) {
292 initial_state->mark_todo(actor.copy.get_buffer());
293 if (reductionMode_ == ReductionMode::dpor) {
294 XBT_DEBUG("Actor %ld is TODO, DPOR is ON so let's go for this one.", actor.copy.get_buffer()->get_pid());
297 XBT_DEBUG("Actor %ld is TODO", actor.copy.get_buffer()->get_pid());
300 stack_.push_back(std::move(initial_state));
303 Checker* create_safety_checker(Session* session)
305 return new SafetyChecker(session);
309 } // namespace simgrid