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"
23 #include "src/mc/mc_request.hpp"
25 #include "src/xbt/mmalloc/mmprivate.h"
27 using api = simgrid::mc::Api;
29 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_safety, mc, "Logging specific to MC safety verification ");
34 void SafetyChecker::check_non_termination(const State* current_state)
36 for (auto state = stack_.rbegin(); state != stack_.rend(); ++state)
37 if (api::get().snapshot_equal((*state)->system_state_.get(), current_state->system_state_.get())) {
38 XBT_INFO("Non-progressive cycle: state %d -> state %d", (*state)->num_, current_state->num_);
39 XBT_INFO("******************************************");
40 XBT_INFO("*** NON-PROGRESSIVE CYCLE DETECTED ***");
41 XBT_INFO("******************************************");
42 XBT_INFO("Counter-example execution trace:");
43 for (auto const& s : get_textual_trace())
44 XBT_INFO(" %s", s.c_str());
45 api::get().dump_record_path();
46 api::get().log_state();
48 throw TerminationError();
52 RecordTrace SafetyChecker::get_record_trace() // override
55 for (auto const& state : stack_)
56 res.push_back(state->get_transition());
60 std::vector<std::string> SafetyChecker::get_textual_trace() // override
62 std::vector<std::string> trace;
63 for (auto const& state : stack_)
64 trace.push_back(state->transition_.textual);
68 void SafetyChecker::log_state() // override
70 XBT_INFO("Expanded states = %lu", expanded_states_count_);
71 XBT_INFO("Visited states = %lu", api::get().mc_get_visited_states());
72 XBT_INFO("Executed transitions = %lu", api::get().mc_get_executed_trans());
75 void SafetyChecker::run()
77 /* This function runs the DFS algorithm the state space.
78 * We do so iteratively instead of recursively, dealing with the call stack manually.
79 * This allows one to explore the call stack at will. */
81 while (not stack_.empty()) {
82 /* Get current state */
83 State* state = stack_.back().get();
85 XBT_DEBUG("**************************************************");
86 XBT_VERB("Exploration depth=%zu (state=%p, num %d)(%zu interleave)", stack_.size(), state, state->num_,
89 api::get().mc_inc_visited_states();
91 // Backtrack if we reached the maximum depth
92 if (stack_.size() > (std::size_t)_sg_mc_max_depth) {
93 XBT_WARN("/!\\ Max depth reached ! /!\\ ");
98 // Backtrack if we are revisiting a state we saw previously
99 if (visited_state_ != nullptr) {
100 XBT_DEBUG("State already visited (equal to state %d), exploration stopped on this path.",
101 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num);
103 visited_state_ = nullptr;
108 // Search an enabled transition in the current state; backtrack if the interleave set is empty
109 // get_request also sets state.transition to be the one corresponding to the returned req
110 smx_simcall_t req = api::get().mc_state_choose_request(state);
111 // req is now the transition of the process that was selected to be executed
113 if (req == nullptr) {
114 XBT_DEBUG("There are no more processes to interleave. (depth %zu)", stack_.size() + 1);
120 // If there are processes to interleave and the maximum depth has not been
121 // reached then perform one step of the exploration algorithm.
122 XBT_DEBUG("Execute: %s", api::get().request_to_string(req, state->transition_.times_considered_).c_str());
125 if (dot_output != nullptr)
126 req_str = api::get().request_get_dot_output(req, state->transition_.times_considered_);
128 api::get().mc_inc_executed_trans();
130 /* Actually answer the request: let execute the selected request (MCed does one step) */
131 api::get().execute(state->transition_, &state->executed_req_);
133 /* Create the new expanded state (copy the state of MCed into our MCer data) */
134 ++expanded_states_count_;
135 auto next_state = std::make_unique<State>(expanded_states_count_);
137 if (_sg_mc_termination)
138 this->check_non_termination(next_state.get());
140 /* Check whether we already explored next_state in the past (but only if interested in state-equality reduction) */
141 if (_sg_mc_max_visited_states > 0)
142 visited_state_ = visited_states_.addVisitedState(expanded_states_count_, next_state.get(), true);
144 /* If this is a new state (or if we don't care about state-equality reduction) */
145 if (visited_state_ == nullptr) {
146 /* Get an enabled process and insert it in the interleave set of the next state */
147 auto actors = api::get().get_actors();
148 for (auto& remoteActor : actors) {
149 auto actor = remoteActor.copy.get_buffer();
150 if (api::get().actor_is_enabled(actor->get_pid())) {
151 next_state->mark_todo(actor);
152 if (reductionMode_ == ReductionMode::dpor)
153 break; // With DPOR, we take the first enabled transition
157 if (dot_output != nullptr)
158 std::fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", state->num_, next_state->num_, req_str.c_str());
160 } else if (dot_output != nullptr)
161 std::fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", state->num_,
162 visited_state_->original_num == -1 ? visited_state_->num : visited_state_->original_num,
165 stack_.push_back(std::move(next_state));
168 XBT_INFO("No property violation found.");
169 api::get().log_state();
172 void SafetyChecker::backtrack()
176 api::get().mc_check_deadlock();
178 /* Traverse the stack backwards until a state with a non empty interleave set is found, deleting all the states that
179 * have it empty in the way. For each deleted state, check if the request that has generated it (from its
180 * predecessor state), depends on any other previous request executed before it. If it does then add it to the
181 * interleave set of the state that executed that previous request. */
183 while (not stack_.empty()) {
184 std::unique_ptr<State> state = std::move(stack_.back());
186 if (reductionMode_ == ReductionMode::dpor) {
187 auto call = state->executed_req_.call_;
188 const kernel::actor::ActorImpl* issuer = api::get().simcall_get_issuer(&state->executed_req_);
189 for (auto i = stack_.rbegin(); i != stack_.rend(); ++i) {
190 State* prev_state = i->get();
191 if (state->executed_req_.issuer_ == prev_state->executed_req_.issuer_) {
192 XBT_DEBUG("Simcall %s and %s with same issuer", SIMIX_simcall_name(call),
193 SIMIX_simcall_name(prev_state->executed_req_.call_));
195 } else if (api::get().simcall_check_dependency(&state->internal_req_, &prev_state->internal_req_)) {
196 if (XBT_LOG_ISENABLED(mc_safety, xbt_log_priority_debug)) {
197 XBT_DEBUG("Dependent Transitions:");
198 int value = prev_state->transition_.times_considered_;
199 smx_simcall_t prev_req = &prev_state->executed_req_;
200 XBT_DEBUG("%s (state=%d)", api::get().request_to_string(prev_req, value).c_str(), prev_state->num_);
201 value = state->transition_.times_considered_;
202 prev_req = &state->executed_req_;
203 XBT_DEBUG("%s (state=%d)", api::get().request_to_string(prev_req, value).c_str(), state->num_);
206 if (not prev_state->actor_states_[issuer->get_pid()].is_done())
207 prev_state->mark_todo(issuer);
209 XBT_DEBUG("Actor %s %ld is in done set", issuer->get_cname(), issuer->get_pid());
212 const kernel::actor::ActorImpl* previous_issuer = api::get().simcall_get_issuer(&prev_state->executed_req_);
213 XBT_DEBUG("Simcall %s, process %ld (state %d) and simcall %s, process %ld (state %d) are independent",
214 SIMIX_simcall_name(call), issuer->get_pid(), state->num_,
215 SIMIX_simcall_name(prev_state->executed_req_.call_), previous_issuer->get_pid(), prev_state->num_);
220 if (state->count_todo() && stack_.size() < (std::size_t)_sg_mc_max_depth) {
221 /* We found a back-tracking point, let's loop */
222 XBT_DEBUG("Back-tracking to state %d at depth %zu", state->num_, stack_.size() + 1);
223 stack_.push_back(std::move(state));
224 this->restore_state();
225 XBT_DEBUG("Back-tracking to state %d at depth %zu done", stack_.back()->num_, stack_.size());
228 XBT_DEBUG("Delete state %d at depth %zu", state->num_, stack_.size() + 1);
233 void SafetyChecker::restore_state()
235 /* Intermediate backtracking */
236 const State* last_state = stack_.back().get();
237 if (last_state->system_state_) {
238 api::get().restore_state(last_state->system_state_);
242 /* Restore the initial state */
243 api::get().restore_initial_state();
245 /* Traverse the stack from the state at position start and re-execute the transitions */
246 for (std::unique_ptr<State> const& state : stack_) {
247 if (state == stack_.back())
249 api::get().execute(state->transition_, &state->executed_req_);
250 /* Update statistics */
251 api::get().mc_inc_visited_states();
252 api::get().mc_inc_executed_trans();
256 SafetyChecker::SafetyChecker() : Checker()
258 reductionMode_ = reduction_mode;
259 if (_sg_mc_termination)
260 reductionMode_ = ReductionMode::none;
261 else if (reductionMode_ == ReductionMode::unset)
262 reductionMode_ = ReductionMode::dpor;
264 if (_sg_mc_termination)
265 XBT_INFO("Check non progressive cycles");
267 XBT_INFO("Check a safety property. Reduction is: %s.",
268 (reductionMode_ == ReductionMode::none ? "none"
269 : (reductionMode_ == ReductionMode::dpor ? "dpor" : "unknown")));
271 api::get().session_initialize();
273 XBT_DEBUG("Starting the safety algorithm");
275 ++expanded_states_count_;
276 auto initial_state = std::make_unique<State>(expanded_states_count_);
278 XBT_DEBUG("**************************************************");
279 XBT_DEBUG("Initial state");
281 /* Get an enabled actor and insert it in the interleave set of the initial state */
282 auto actors = api::get().get_actors();
283 for (auto& actor : actors)
284 if (api::get().actor_is_enabled(actor.copy.get_buffer()->get_pid())) {
285 initial_state->mark_todo(actor.copy.get_buffer());
286 if (reductionMode_ != ReductionMode::none)
290 stack_.push_back(std::move(initial_state));
293 Checker* createSafetyChecker()
295 return new SafetyChecker();
299 } // namespace simgrid