1 /* Copyright (c) 2016-2021. 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. */
14 #include <xbt/sysdep.h>
16 #include "src/mc/Transition.hpp"
17 #include "src/mc/VisitedState.hpp"
18 #include "src/mc/checker/SafetyChecker.hpp"
19 #include "src/mc/mc_config.hpp"
20 #include "src/mc/mc_exit.hpp"
21 #include "src/mc/mc_private.hpp"
22 #include "src/mc/mc_record.hpp"
24 #include "src/xbt/mmalloc/mmprivate.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 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
97 // Backtrack if we are revisiting a state we saw previously
98 if (visited_state_ != nullptr) {
99 XBT_DEBUG("State already visited (equal to state %d), exploration stopped on this path.",
100 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num);
102 visited_state_ = nullptr;
107 // Search an enabled transition in the current state; backtrack if the interleave set is empty
108 // get_request also sets state.transition to be the one corresponding to the returned req
109 smx_simcall_t req = api::get().mc_state_choose_request(state);
110 // req is now the transition of the process that was selected to be executed
112 if (req == nullptr) {
113 XBT_DEBUG("There are no more processes to interleave. (depth %zu)", stack_.size() + 1);
119 // If there are processes to interleave and the maximum depth has not been
120 // reached then perform one step of the exploration algorithm.
121 XBT_DEBUG("Execute: %s", api::get().request_to_string(req, state->transition_.times_considered_).c_str());
124 if (dot_output != nullptr)
125 req_str = api::get().request_get_dot_output(req, state->transition_.times_considered_);
127 api::get().mc_inc_executed_trans();
129 /* Actually answer the request: let execute the selected request (MCed does one step) */
130 api::get().execute(state->transition_, &state->executed_req_);
132 /* Create the new expanded state (copy the state of MCed into our MCer data) */
133 ++expanded_states_count_;
134 auto next_state = std::make_unique<State>(expanded_states_count_);
136 if (_sg_mc_termination)
137 this->check_non_termination(next_state.get());
139 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
140 if (_sg_mc_max_visited_states > 0)
141 visited_state_ = visited_states_.addVisitedState(expanded_states_count_, next_state.get(), true);
143 /* If this is a new state (or if we don't care about state-equality reduction) */
144 if (visited_state_ == nullptr) {
145 /* Get an enabled process and insert it in the interleave set of the next state */
146 auto actors = api::get().get_actors();
147 for (auto& remoteActor : actors) {
148 auto actor = remoteActor.copy.get_buffer();
149 if (api::get().actor_is_enabled(actor->get_pid())) {
150 next_state->mark_todo(actor);
151 if (reductionMode_ == ReductionMode::dpor)
152 break; // With DPOR, we take the first enabled transition
156 if (dot_output != nullptr)
157 std::fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", state->num_, next_state->num_, req_str.c_str());
159 } else if (dot_output != nullptr)
160 std::fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", state->num_,
161 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num,
164 stack_.push_back(std::move(next_state));
167 XBT_INFO("No property violation found.");
168 api::get().log_state();
171 void SafetyChecker::backtrack()
175 api::get().mc_check_deadlock();
177 /* Traverse the stack backwards until a state with a non empty interleave set is found, deleting all the states that
178 * have it empty in the way. For each deleted state, check if the request that has generated it (from its
179 * predecessor state), depends on any other previous request executed before it. If it does then add it to the
180 * interleave set of the state that executed that previous request. */
182 while (not stack_.empty()) {
183 std::unique_ptr<State> state = std::move(stack_.back());
185 if (reductionMode_ == ReductionMode::dpor) {
186 auto call = state->executed_req_.call_;
187 const kernel::actor::ActorImpl* issuer = api::get().simcall_get_issuer(&state->executed_req_);
188 for (auto i = stack_.rbegin(); i != stack_.rend(); ++i) {
189 State* prev_state = i->get();
190 if (state->executed_req_.issuer_ == prev_state->executed_req_.issuer_) {
191 XBT_DEBUG("Simcall %s and %s with same issuer", SIMIX_simcall_name(call),
192 SIMIX_simcall_name(prev_state->executed_req_.call_));
194 } else if (api::get().simcall_check_dependency(&state->internal_req_, &prev_state->internal_req_)) {
195 if (XBT_LOG_ISENABLED(mc_safety, xbt_log_priority_debug)) {
196 XBT_DEBUG("Dependent Transitions:");
197 int value = prev_state->transition_.times_considered_;
198 smx_simcall_t prev_req = &prev_state->executed_req_;
199 XBT_DEBUG("%s (state=%d)", api::get().request_to_string(prev_req, value).c_str(), prev_state->num_);
200 value = state->transition_.times_considered_;
201 prev_req = &state->executed_req_;
202 XBT_DEBUG("%s (state=%d)", api::get().request_to_string(prev_req, value).c_str(), state->num_);
205 if (not prev_state->actor_states_[issuer->get_pid()].is_done())
206 prev_state->mark_todo(issuer);
208 XBT_DEBUG("Actor %s %ld is in done set", issuer->get_cname(), issuer->get_pid());
211 const kernel::actor::ActorImpl* previous_issuer = api::get().simcall_get_issuer(&prev_state->executed_req_);
212 XBT_DEBUG("Simcall %s, process %ld (state %d) and simcall %s, process %ld (state %d) are independent",
213 SIMIX_simcall_name(call), issuer->get_pid(), state->num_,
214 SIMIX_simcall_name(prev_state->executed_req_.call_), previous_issuer->get_pid(), prev_state->num_);
219 if (state->count_todo() && stack_.size() < (std::size_t)_sg_mc_max_depth) {
220 /* We found a back-tracking point, let's loop */
221 XBT_DEBUG("Back-tracking to state %d at depth %zu", state->num_, stack_.size() + 1);
222 stack_.push_back(std::move(state));
223 this->restore_state();
224 XBT_DEBUG("Back-tracking to state %d at depth %zu done", stack_.back()->num_, stack_.size());
227 XBT_DEBUG("Delete state %d at depth %zu", state->num_, stack_.size() + 1);
232 void SafetyChecker::restore_state()
234 /* Intermediate backtracking */
235 const State* last_state = stack_.back().get();
236 if (last_state->system_state_) {
237 api::get().restore_state(last_state->system_state_);
241 /* Restore the initial state */
242 api::get().restore_initial_state();
244 /* Traverse the stack from the state at position start and re-execute the transitions */
245 for (std::unique_ptr<State> const& state : stack_) {
246 if (state == stack_.back())
248 api::get().execute(state->transition_, &state->executed_req_);
249 /* Update statistics */
250 api::get().mc_inc_visited_states();
251 api::get().mc_inc_executed_trans();
255 SafetyChecker::SafetyChecker(Session* session) : Checker(session)
257 reductionMode_ = reduction_mode;
258 if (_sg_mc_termination)
259 reductionMode_ = ReductionMode::none;
260 else if (reductionMode_ == ReductionMode::unset)
261 reductionMode_ = ReductionMode::dpor;
263 if (_sg_mc_termination)
264 XBT_INFO("Check non progressive cycles");
266 XBT_INFO("Check a safety property. Reduction is: %s.",
267 (reductionMode_ == ReductionMode::none ? "none"
268 : (reductionMode_ == ReductionMode::dpor ? "dpor" : "unknown")));
270 api::get().session_initialize();
272 XBT_DEBUG("Starting the safety algorithm");
274 ++expanded_states_count_;
275 auto initial_state = std::make_unique<State>(expanded_states_count_);
277 XBT_DEBUG("**************************************************");
278 XBT_DEBUG("Initial state");
280 /* Get an enabled actor and insert it in the interleave set of the initial state */
281 auto actors = api::get().get_actors();
282 for (auto& actor : actors)
283 if (api::get().actor_is_enabled(actor.copy.get_buffer()->get_pid())) {
284 initial_state->mark_todo(actor.copy.get_buffer());
285 if (reductionMode_ != ReductionMode::none)
289 stack_.push_back(std::move(initial_state));
292 Checker* createSafetyChecker(Session* session)
294 return new SafetyChecker(session);
298 } // namespace simgrid