#include <stdio.h>
+#include <algorithm>
+#include <mutex>
+#include <new>
#include "model.h"
#include "action.h"
#include "clockvector.h"
#include "cyclegraph.h"
#include "promise.h"
+#include "datarace.h"
+#include "threads-model.h"
+#include "output.h"
#define INITIAL_THREAD_ID 0
ModelChecker *model;
+struct bug_message {
+ bug_message(const char *str) {
+ const char *fmt = " [BUG] %s\n";
+ msg = (char *)snapshot_malloc(strlen(fmt) + strlen(str));
+ sprintf(msg, fmt, str);
+ }
+ ~bug_message() { if (msg) snapshot_free(msg); }
+
+ char *msg;
+ void print() { model_print("%s", msg); }
+
+ SNAPSHOTALLOC
+};
+
+/**
+ * Structure for holding small ModelChecker members that should be snapshotted
+ */
+struct model_snapshot_members {
+ model_snapshot_members() :
+ /* First thread created will have id INITIAL_THREAD_ID */
+ next_thread_id(INITIAL_THREAD_ID),
+ used_sequence_numbers(0),
+ next_backtrack(NULL),
+ bugs(),
+ stats(),
+ failed_promise(false),
+ too_many_reads(false),
+ no_valid_reads(false),
+ bad_synchronization(false),
+ asserted(false)
+ { }
+
+ ~model_snapshot_members() {
+ for (unsigned int i = 0; i < bugs.size(); i++)
+ delete bugs[i];
+ bugs.clear();
+ }
+
+ unsigned int next_thread_id;
+ modelclock_t used_sequence_numbers;
+ ModelAction *next_backtrack;
+ std::vector< bug_message *, SnapshotAlloc<bug_message *> > bugs;
+ struct execution_stats stats;
+ bool failed_promise;
+ bool too_many_reads;
+ bool no_valid_reads;
+ /** @brief Incorrectly-ordered synchronization was made */
+ bool bad_synchronization;
+ bool asserted;
+
+ SNAPSHOTALLOC
+};
+
/** @brief Constructor */
ModelChecker::ModelChecker(struct model_params params) :
/* Initialize default scheduler */
- scheduler(new Scheduler()),
- /* First thread created will have id INITIAL_THREAD_ID */
- next_thread_id(INITIAL_THREAD_ID),
- used_sequence_numbers(0),
- num_executions(0),
params(params),
- current_action(NULL),
+ scheduler(new Scheduler()),
diverge(NULL),
- nextThread(THREAD_ID_T_NONE),
+ earliest_diverge(NULL),
action_trace(new action_list_t()),
thread_map(new HashTable<int, Thread *, int>()),
- obj_map(new HashTable<const void *, action_list_t, uintptr_t, 4>()),
- obj_thrd_map(new HashTable<void *, std::vector<action_list_t>, uintptr_t, 4 >()),
- promises(new std::vector<Promise *>()),
- thrd_last_action(new std::vector<ModelAction *>(1)),
+ obj_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
+ lock_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
+ condvar_waiters_map(new HashTable<const void *, action_list_t *, uintptr_t, 4>()),
+ obj_thrd_map(new HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4 >()),
+ promises(new std::vector< Promise *, SnapshotAlloc<Promise *> >()),
+ futurevalues(new std::vector< struct PendingFutureValue, SnapshotAlloc<struct PendingFutureValue> >()),
+ pending_rel_seqs(new std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >()),
+ thrd_last_action(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >(1)),
+ thrd_last_fence_release(new std::vector< ModelAction *, SnapshotAlloc<ModelAction *> >()),
node_stack(new NodeStack()),
- next_backtrack(NULL),
- mo_graph(new CycleGraph()),
- failed_promise(false)
+ priv(new struct model_snapshot_members()),
+ mo_graph(new CycleGraph())
{
+ /* Initialize a model-checker thread, for special ModelActions */
+ model_thread = new Thread(get_next_id());
+ thread_map->put(id_to_int(model_thread->get_id()), model_thread);
}
/** @brief Destructor */
ModelChecker::~ModelChecker()
{
- for (int i = 0; i < get_num_threads(); i++)
+ for (unsigned int i = 0; i < get_num_threads(); i++)
delete thread_map->get(i);
delete thread_map;
delete obj_thrd_map;
delete obj_map;
+ delete lock_waiters_map;
+ delete condvar_waiters_map;
delete action_trace;
for (unsigned int i = 0; i < promises->size(); i++)
delete (*promises)[i];
delete promises;
+ delete pending_rel_seqs;
+
delete thrd_last_action;
+ delete thrd_last_fence_release;
delete node_stack;
delete scheduler;
delete mo_graph;
+ delete priv;
+}
+
+static action_list_t * get_safe_ptr_action(HashTable<const void *, action_list_t *, uintptr_t, 4> * hash, void * ptr)
+{
+ action_list_t *tmp = hash->get(ptr);
+ if (tmp == NULL) {
+ tmp = new action_list_t();
+ hash->put(ptr, tmp);
+ }
+ return tmp;
+}
+
+static std::vector<action_list_t> * get_safe_ptr_vect_action(HashTable<void *, std::vector<action_list_t> *, uintptr_t, 4> * hash, void * ptr)
+{
+ std::vector<action_list_t> *tmp = hash->get(ptr);
+ if (tmp == NULL) {
+ tmp = new std::vector<action_list_t>();
+ hash->put(ptr, tmp);
+ }
+ return tmp;
}
/**
{
DEBUG("+++ Resetting to initial state +++\n");
node_stack->reset_execution();
- current_action = NULL;
- next_thread_id = INITIAL_THREAD_ID;
- used_sequence_numbers = 0;
- nextThread = 0;
- next_backtrack = NULL;
- failed_promise = false;
- snapshotObject->backTrackBeforeStep(0);
-}
-/** @returns a thread ID for a new Thread */
-thread_id_t ModelChecker::get_next_id()
-{
- return next_thread_id++;
+ /* Print all model-checker output before rollback */
+ fflush(model_out);
+
+ /**
+ * FIXME: if we utilize partial rollback, we will need to free only
+ * those pending actions which were NOT pending before the rollback
+ * point
+ */
+ for (unsigned int i = 0; i < get_num_threads(); i++)
+ delete get_thread(int_to_id(i))->get_pending();
+
+ snapshot_backtrack_before(0);
}
-/** @returns the number of user threads created during this execution */
-int ModelChecker::get_num_threads()
+/** @return a thread ID for a new Thread */
+thread_id_t ModelChecker::get_next_id()
{
- return next_thread_id;
+ return priv->next_thread_id++;
}
-/** @returns a sequence number for a new ModelAction */
-modelclock_t ModelChecker::get_next_seq_num()
+/** @return the number of user threads created during this execution */
+unsigned int ModelChecker::get_num_threads() const
{
- return ++used_sequence_numbers;
+ return priv->next_thread_id;
}
/**
- * Performs the "scheduling" for the model-checker. That is, it checks if the
- * model-checker has selected a "next thread to run" and returns it, if
- * available. This function should be called from the Scheduler routine, where
- * the Scheduler falls back to a default scheduling routine if needed.
+ * Must be called from user-thread context (e.g., through the global
+ * thread_current() interface)
*
- * @return The next thread chosen by the model-checker. If the model-checker
- * makes no selection, retuns NULL.
+ * @return The currently executing Thread.
*/
-Thread * ModelChecker::schedule_next_thread()
+Thread * ModelChecker::get_current_thread() const
{
- Thread *t;
- if (nextThread == THREAD_ID_T_NONE)
- return NULL;
- t = thread_map->get(id_to_int(nextThread));
+ return scheduler->get_current_thread();
+}
- ASSERT(t != NULL);
+/** @return a sequence number for a new ModelAction */
+modelclock_t ModelChecker::get_next_seq_num()
+{
+ return ++priv->used_sequence_numbers;
+}
- return t;
+Node * ModelChecker::get_curr_node() const
+{
+ return node_stack->get_head();
}
/**
- * Choose the next thread in the replay sequence.
+ * @brief Choose the next thread to execute.
+ *
+ * This function chooses the next thread that should execute. It can force the
+ * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be
+ * followed by a THREAD_START, or it can enforce execution replay/backtracking.
+ * The model-checker may have no preference regarding the next thread (i.e.,
+ * when exploring a new execution ordering), in which case we defer to the
+ * scheduler.
*
- * If the replay sequence has reached the 'diverge' point, returns a thread
- * from the backtracking set. Otherwise, simply returns the next thread in the
- * sequence that is being replayed.
+ * @param curr Optional: The current ModelAction. Only used if non-NULL and it
+ * might guide the choice of next thread (i.e., THREAD_CREATE should be
+ * followed by THREAD_START, or ATOMIC_RMWR followed by ATOMIC_{RMW,RMWC})
+ * @return The next chosen thread to run, if any exist. Or else if no threads
+ * remain to be executed, return NULL.
*/
-thread_id_t ModelChecker::get_next_replay_thread()
+Thread * ModelChecker::get_next_thread(ModelAction *curr)
{
thread_id_t tid;
- /* Have we completed exploring the preselected path? */
+ if (curr != NULL) {
+ /* Do not split atomic actions. */
+ if (curr->is_rmwr())
+ return get_thread(curr);
+ else if (curr->get_type() == THREAD_CREATE)
+ return curr->get_thread_operand();
+ }
+
+ /*
+ * Have we completed exploring the preselected path? Then let the
+ * scheduler decide
+ */
if (diverge == NULL)
- return THREAD_ID_T_NONE;
+ return scheduler->select_next_thread();
/* Else, we are trying to replay an execution */
ModelAction *next = node_stack->get_next()->get_action();
if (next == diverge) {
+ if (earliest_diverge == NULL || *diverge < *earliest_diverge)
+ earliest_diverge = diverge;
+
Node *nextnode = next->get_node();
+ Node *prevnode = nextnode->get_parent();
+ scheduler->update_sleep_set(prevnode);
+
/* Reached divergence point */
- if (nextnode->increment_promise()) {
+ if (nextnode->increment_misc()) {
+ /* The next node will try to satisfy a different misc_index values. */
+ tid = next->get_tid();
+ node_stack->pop_restofstack(2);
+ } else if (nextnode->increment_promise()) {
/* The next node will try to satisfy a different set of promises. */
tid = next->get_tid();
node_stack->pop_restofstack(2);
/* The next node will try to read from a different future value. */
tid = next->get_tid();
node_stack->pop_restofstack(2);
+ } else if (nextnode->increment_relseq_break()) {
+ /* The next node will try to resolve a release sequence differently */
+ tid = next->get_tid();
+ node_stack->pop_restofstack(2);
} else {
+ ASSERT(prevnode);
/* Make a different thread execute for next step */
- Node *node = nextnode->get_parent();
- tid = node->get_next_backtrack();
+ scheduler->add_sleep(get_thread(next->get_tid()));
+ tid = prevnode->get_next_backtrack();
+ /* Make sure the backtracked thread isn't sleeping. */
node_stack->pop_restofstack(1);
+ if (diverge == earliest_diverge) {
+ earliest_diverge = prevnode->get_action();
+ }
}
+ /* The correct sleep set is in the parent node. */
+ execute_sleep_set();
+
DEBUG("*** Divergence point ***\n");
+
diverge = NULL;
} else {
tid = next->get_tid();
}
- DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
- return tid;
+ DEBUG("*** ModelChecker chose next thread = %d ***\n", id_to_int(tid));
+ ASSERT(tid != THREAD_ID_T_NONE);
+ return thread_map->get(id_to_int(tid));
}
/**
- * Queries the model-checker for more executions to explore and, if one
- * exists, resets the model-checker state to execute a new execution.
- *
- * @return If there are more executions to explore, return true. Otherwise,
- * return false.
+ * We need to know what the next actions of all threads in the sleep
+ * set will be. This method computes them and stores the actions at
+ * the corresponding thread object's pending action.
*/
-bool ModelChecker::next_execution()
-{
- DBG();
-
- num_executions++;
- if (isfinalfeasible() || DBG_ENABLED())
- print_summary();
+void ModelChecker::execute_sleep_set()
+{
+ for (unsigned int i = 0; i < get_num_threads(); i++) {
+ thread_id_t tid = int_to_id(i);
+ Thread *thr = get_thread(tid);
+ if (scheduler->is_sleep_set(thr) && thr->get_pending()) {
+ thr->get_pending()->set_sleep_flag();
+ }
+ }
+}
- if ((diverge = model->get_next_backtrack()) == NULL)
+/**
+ * @brief Should the current action wake up a given thread?
+ *
+ * @param curr The current action
+ * @param thread The thread that we might wake up
+ * @return True, if we should wake up the sleeping thread; false otherwise
+ */
+bool ModelChecker::should_wake_up(const ModelAction *curr, const Thread *thread) const
+{
+ const ModelAction *asleep = thread->get_pending();
+ /* Don't allow partial RMW to wake anyone up */
+ if (curr->is_rmwr())
return false;
-
- if (DBG_ENABLED()) {
- printf("Next execution will diverge at:\n");
- diverge->print();
+ /* Synchronizing actions may have been backtracked */
+ if (asleep->could_synchronize_with(curr))
+ return true;
+ /* All acquire/release fences and fence-acquire/store-release */
+ if (asleep->is_fence() && asleep->is_acquire() && curr->is_release())
+ return true;
+ /* Fence-release + store can awake load-acquire on the same location */
+ if (asleep->is_read() && asleep->is_acquire() && curr->same_var(asleep) && curr->is_write()) {
+ ModelAction *fence_release = get_last_fence_release(curr->get_tid());
+ if (fence_release && *(get_last_action(thread->get_id())) < *fence_release)
+ return true;
}
-
- model->reset_to_initial_state();
- return true;
+ return false;
}
-ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
+void ModelChecker::wake_up_sleeping_actions(ModelAction *curr)
{
- action_type type = act->get_type();
-
- switch (type) {
- case ATOMIC_READ:
- case ATOMIC_WRITE:
- case ATOMIC_RMW:
- break;
- default:
- return NULL;
- }
- /* linear search: from most recent to oldest */
- action_list_t *list = obj_map->get_safe_ptr(act->get_location());
- action_list_t::reverse_iterator rit;
- for (rit = list->rbegin(); rit != list->rend(); rit++) {
- ModelAction *prev = *rit;
- if (act->is_synchronizing(prev))
- return prev;
+ for (unsigned int i = 0; i < get_num_threads(); i++) {
+ Thread *thr = get_thread(int_to_id(i));
+ if (scheduler->is_sleep_set(thr)) {
+ if (should_wake_up(curr, thr))
+ /* Remove this thread from sleep set */
+ scheduler->remove_sleep(thr);
+ }
}
- return NULL;
}
-void ModelChecker::set_backtracking(ModelAction *act)
+/** @brief Alert the model-checker that an incorrectly-ordered
+ * synchronization was made */
+void ModelChecker::set_bad_synchronization()
{
- ModelAction *prev;
- Node *node;
- Thread *t = get_thread(act->get_tid());
+ priv->bad_synchronization = true;
+}
- prev = get_last_conflict(act);
- if (prev == NULL)
- return;
+/**
+ * Check whether the current trace has triggered an assertion which should halt
+ * its execution.
+ *
+ * @return True, if the execution should be aborted; false otherwise
+ */
+bool ModelChecker::has_asserted() const
+{
+ return priv->asserted;
+}
- node = prev->get_node()->get_parent();
+/**
+ * Trigger a trace assertion which should cause this execution to be halted.
+ * This can be due to a detected bug or due to an infeasibility that should
+ * halt ASAP.
+ */
+void ModelChecker::set_assert()
+{
+ priv->asserted = true;
+}
- while (!node->is_enabled(t))
- t = t->get_parent();
+/**
+ * Check if we are in a deadlock. Should only be called at the end of an
+ * execution, although it should not give false positives in the middle of an
+ * execution (there should be some ENABLED thread).
+ *
+ * @return True if program is in a deadlock; false otherwise
+ */
+bool ModelChecker::is_deadlocked() const
+{
+ bool blocking_threads = false;
+ for (unsigned int i = 0; i < get_num_threads(); i++) {
+ thread_id_t tid = int_to_id(i);
+ if (is_enabled(tid))
+ return false;
+ Thread *t = get_thread(tid);
+ if (!t->is_model_thread() && t->get_pending())
+ blocking_threads = true;
+ }
+ return blocking_threads;
+}
- /* Check if this has been explored already */
- if (node->has_been_explored(t->get_id()))
- return;
+/**
+ * Check if this is a complete execution. That is, have all thread completed
+ * execution (rather than exiting because sleep sets have forced a redundant
+ * execution).
+ *
+ * @return True if the execution is complete.
+ */
+bool ModelChecker::is_complete_execution() const
+{
+ for (unsigned int i = 0; i < get_num_threads(); i++)
+ if (is_enabled(int_to_id(i)))
+ return false;
+ return true;
+}
- /* Cache the latest backtracking point */
- if (!next_backtrack || *prev > *next_backtrack)
- next_backtrack = prev;
+/**
+ * @brief Assert a bug in the executing program.
+ *
+ * Use this function to assert any sort of bug in the user program. If the
+ * current trace is feasible (actually, a prefix of some feasible execution),
+ * then this execution will be aborted, printing the appropriate message. If
+ * the current trace is not yet feasible, the error message will be stashed and
+ * printed if the execution ever becomes feasible.
+ *
+ * @param msg Descriptive message for the bug (do not include newline char)
+ * @return True if bug is immediately-feasible
+ */
+bool ModelChecker::assert_bug(const char *msg)
+{
+ priv->bugs.push_back(new bug_message(msg));
- /* If this is a new backtracking point, mark the tree */
- if (!node->set_backtrack(t->get_id()))
- return;
- DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
- prev->get_tid(), t->get_id());
- if (DBG_ENABLED()) {
- prev->print();
- act->print();
+ if (isfeasibleprefix()) {
+ set_assert();
+ return true;
}
+ return false;
}
/**
- * Returns last backtracking point. The model checker will explore a different
- * path for this point in the next execution.
- * @return The ModelAction at which the next execution should diverge.
+ * @brief Assert a bug in the executing program, asserted by a user thread
+ * @see ModelChecker::assert_bug
+ * @param msg Descriptive message for the bug (do not include newline char)
*/
-ModelAction * ModelChecker::get_next_backtrack()
+void ModelChecker::assert_user_bug(const char *msg)
{
- ModelAction *next = next_backtrack;
- next_backtrack = NULL;
- return next;
+ /* If feasible bug, bail out now */
+ if (assert_bug(msg))
+ switch_to_master(NULL);
}
-void ModelChecker::check_current_action(void)
+/** @return True, if any bugs have been reported for this execution */
+bool ModelChecker::have_bug_reports() const
{
- ModelAction *curr = this->current_action;
- bool already_added = false;
- this->current_action = NULL;
- if (!curr) {
- DEBUG("trying to push NULL action...\n");
- return;
- }
+ return priv->bugs.size() != 0;
+}
- if (curr->is_rmwc() || curr->is_rmw()) {
- ModelAction *tmp = process_rmw(curr);
- already_added = true;
- delete curr;
- curr = tmp;
- } else {
- ModelAction *tmp = node_stack->explore_action(curr);
- if (tmp) {
- /* Discard duplicate ModelAction; use action from NodeStack */
- /* First restore type and order in case of RMW operation */
- if (curr->is_rmwr())
- tmp->copy_typeandorder(curr);
-
- /* If we have diverged, we need to reset the clock vector. */
- if (diverge == NULL)
- tmp->create_cv(get_parent_action(tmp->get_tid()));
-
- delete curr;
- curr = tmp;
- } else {
- /*
- * Perform one-time actions when pushing new ModelAction onto
- * NodeStack
- */
- curr->create_cv(get_parent_action(curr->get_tid()));
- /* Build may_read_from set */
- if (curr->is_read())
- build_reads_from_past(curr);
- if (curr->is_write())
- compute_promises(curr);
- }
+/** @brief Print bug report listing for this execution (if any bugs exist) */
+void ModelChecker::print_bugs() const
+{
+ if (have_bug_reports()) {
+ model_print("Bug report: %zu bug%s detected\n",
+ priv->bugs.size(),
+ priv->bugs.size() > 1 ? "s" : "");
+ for (unsigned int i = 0; i < priv->bugs.size(); i++)
+ priv->bugs[i]->print();
}
+}
- /* Assign 'creation' parent */
- if (curr->get_type() == THREAD_CREATE) {
- Thread *th = (Thread *)curr->get_location();
- th->set_creation(curr);
- }
+/**
+ * @brief Record end-of-execution stats
+ *
+ * Must be run when exiting an execution. Records various stats.
+ * @see struct execution_stats
+ */
+void ModelChecker::record_stats()
+{
+ stats.num_total++;
+ if (!isfeasibleprefix())
+ stats.num_infeasible++;
+ else if (have_bug_reports())
+ stats.num_buggy_executions++;
+ else if (is_complete_execution())
+ stats.num_complete++;
+ else
+ stats.num_redundant++;
+}
- /* Deal with new thread */
- if (curr->get_type() == THREAD_START)
- check_promises(NULL, curr->get_cv());
+/** @brief Print execution stats */
+void ModelChecker::print_stats() const
+{
+ model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
+ model_print("Number of redundant executions: %d\n", stats.num_redundant);
+ model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
+ model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
+ model_print("Total executions: %d\n", stats.num_total);
+ model_print("Total nodes created: %d\n", node_stack->get_total_nodes());
+}
- /* Assign reads_from values */
- Thread *th = get_thread(curr->get_tid());
- uint64_t value = VALUE_NONE;
- if (curr->is_read()) {
- const ModelAction *reads_from = curr->get_node()->get_read_from();
- if (reads_from != NULL) {
- value = reads_from->get_value();
- /* Assign reads_from, perform release/acquire synchronization */
- curr->read_from(reads_from);
- r_modification_order(curr,reads_from);
- } else {
- /* Read from future value */
- value = curr->get_node()->get_future_value();
- curr->read_from(NULL);
- Promise *valuepromise = new Promise(curr, value);
- promises->push_back(valuepromise);
- }
- } else if (curr->is_write()) {
- w_modification_order(curr);
- resolve_promises(curr);
+/**
+ * @brief End-of-exeuction print
+ * @param printbugs Should any existing bugs be printed?
+ */
+void ModelChecker::print_execution(bool printbugs) const
+{
+ print_program_output();
+
+ if (DBG_ENABLED() || params.verbose) {
+ model_print("Earliest divergence point since last feasible execution:\n");
+ if (earliest_diverge)
+ earliest_diverge->print();
+ else
+ model_print("(Not set)\n");
+
+ model_print("\n");
+ print_stats();
}
- th->set_return_value(value);
+ /* Don't print invalid bugs */
+ if (printbugs)
+ print_bugs();
- /* Add action to list. */
- if (!already_added)
- add_action_to_lists(curr);
+ model_print("\n");
+ print_summary();
+}
- /** @todo Is there a better interface for setting the next thread rather
- than this field/convoluted approach? Perhaps like just returning
- it or something? */
+/**
+ * Queries the model-checker for more executions to explore and, if one
+ * exists, resets the model-checker state to execute a new execution.
+ *
+ * @return If there are more executions to explore, return true. Otherwise,
+ * return false.
+ */
+bool ModelChecker::next_execution()
+{
+ DBG();
+ /* Is this execution a feasible execution that's worth bug-checking? */
+ bool complete = isfeasibleprefix() && (is_complete_execution() ||
+ have_bug_reports());
- /* Do not split atomic actions. */
- if (curr->is_rmwr())
- nextThread = thread_current()->get_id();
- else
- nextThread = get_next_replay_thread();
+ /* End-of-execution bug checks */
+ if (complete) {
+ if (is_deadlocked())
+ assert_bug("Deadlock detected");
- Node *currnode = curr->get_node();
- Node *parnode = currnode->get_parent();
+ checkDataRaces();
+ }
- if (!parnode->backtrack_empty() || !currnode->read_from_empty() ||
- !currnode->future_value_empty() || !currnode->promise_empty())
- if (!next_backtrack || *curr > *next_backtrack)
- next_backtrack = curr;
+ record_stats();
- set_backtracking(curr);
-}
+ /* Output */
+ if (DBG_ENABLED() || params.verbose || (complete && have_bug_reports()))
+ print_execution(complete);
+ else
+ clear_program_output();
-/** @returns whether the current partial trace is feasible. */
-bool ModelChecker::isfeasible() {
- return !mo_graph->checkForCycles() && !failed_promise;
-}
+ if (complete)
+ earliest_diverge = NULL;
-/** Returns whether the current completed trace is feasible. */
-bool ModelChecker::isfinalfeasible() {
- return isfeasible() && promises->size() == 0;
-}
+ if ((diverge = get_next_backtrack()) == NULL)
+ return false;
-/** Close out a RMWR by converting previous RMWR into a RMW or READ. */
-ModelAction * ModelChecker::process_rmw(ModelAction *act) {
- int tid = id_to_int(act->get_tid());
- ModelAction *lastread = get_last_action(tid);
- lastread->process_rmw(act);
- if (act->is_rmw())
- mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
- return lastread;
+ if (DBG_ENABLED()) {
+ model_print("Next execution will diverge at:\n");
+ diverge->print();
+ }
+
+ reset_to_initial_state();
+ return true;
}
/**
- * Updates the mo_graph with the constraints imposed from the current read.
- * @param curr The current action. Must be a read.
- * @param rf The action that curr reads from. Must be a write.
- * @return True if modification order edges were added; false otherwise
+ * @brief Find the last fence-related backtracking conflict for a ModelAction
+ *
+ * This function performs the search for the most recent conflicting action
+ * against which we should perform backtracking, as affected by fence
+ * operations. This includes pairs of potentially-synchronizing actions which
+ * occur due to fence-acquire or fence-release, and hence should be explored in
+ * the opposite execution order.
+ *
+ * @param act The current action
+ * @return The most recent action which conflicts with act due to fences
*/
-bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf)
+ModelAction * ModelChecker::get_last_fence_conflict(ModelAction *act) const
{
- std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
- unsigned int i;
- bool added = false;
- ASSERT(curr->is_read());
+ /* Only perform release/acquire fence backtracking for stores */
+ if (!act->is_write())
+ return NULL;
- /* Iterate over all threads */
- for (i = 0; i < thrd_lists->size(); i++) {
- /* Iterate over actions in thread, starting from most recent */
- action_list_t *list = &(*thrd_lists)[i];
- action_list_t::reverse_iterator rit;
- for (rit = list->rbegin(); rit != list->rend(); rit++) {
- ModelAction *act = *rit;
+ /* Find a fence-release (or, act is a release) */
+ ModelAction *last_release;
+ if (act->is_release())
+ last_release = act;
+ else
+ last_release = get_last_fence_release(act->get_tid());
+ if (!last_release)
+ return NULL;
- /* Include at most one act per-thread that "happens before" curr */
- if (act->happens_before(curr)) {
- if (act->is_read()) {
- const ModelAction *prevreadfrom = act->get_reads_from();
- if (prevreadfrom != NULL && rf != prevreadfrom) {
- mo_graph->addEdge(prevreadfrom, rf);
- added = true;
- }
- } else if (rf != act) {
- mo_graph->addEdge(act, rf);
- added = true;
- }
- break;
+ /* Skip past the release */
+ action_list_t *list = action_trace;
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++)
+ if (*rit == last_release)
+ break;
+ ASSERT(rit != list->rend());
+
+ /* Find a prior:
+ * load-acquire
+ * or
+ * load --sb-> fence-acquire */
+ std::vector< ModelAction *, ModelAlloc<ModelAction *> > acquire_fences(get_num_threads(), NULL);
+ std::vector< ModelAction *, ModelAlloc<ModelAction *> > prior_loads(get_num_threads(), NULL);
+ bool found_acquire_fences = false;
+ for ( ; rit != list->rend(); rit++) {
+ ModelAction *prev = *rit;
+ if (act->same_thread(prev))
+ continue;
+
+ int tid = id_to_int(prev->get_tid());
+
+ if (prev->is_read() && act->same_var(prev)) {
+ if (prev->is_acquire()) {
+ /* Found most recent load-acquire, don't need
+ * to search for more fences */
+ if (!found_acquire_fences)
+ return NULL;
+ } else {
+ prior_loads[tid] = prev;
}
}
+ if (prev->is_acquire() && prev->is_fence() && !acquire_fences[tid]) {
+ found_acquire_fences = true;
+ acquire_fences[tid] = prev;
+ }
}
- return added;
+ ModelAction *latest_backtrack = NULL;
+ for (unsigned int i = 0; i < acquire_fences.size(); i++)
+ if (acquire_fences[i] && prior_loads[i])
+ if (!latest_backtrack || *latest_backtrack < *acquire_fences[i])
+ latest_backtrack = acquire_fences[i];
+ return latest_backtrack;
}
-/** Updates the mo_graph with the constraints imposed from the current read. */
-void ModelChecker::post_r_modification_order(ModelAction *curr, const ModelAction *rf)
+/**
+ * @brief Find the last backtracking conflict for a ModelAction
+ *
+ * This function performs the search for the most recent conflicting action
+ * against which we should perform backtracking. This primary includes pairs of
+ * synchronizing actions which should be explored in the opposite execution
+ * order.
+ *
+ * @param act The current action
+ * @return The most recent action which conflicts with act
+ */
+ModelAction * ModelChecker::get_last_conflict(ModelAction *act) const
{
- std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
- unsigned int i;
- ASSERT(curr->is_read());
-
- /* Iterate over all threads */
- for (i = 0; i < thrd_lists->size(); i++) {
- /* Iterate over actions in thread, starting from most recent */
- action_list_t *list = &(*thrd_lists)[i];
+ switch (act->get_type()) {
+ /* case ATOMIC_FENCE: fences don't directly cause backtracking */
+ case ATOMIC_READ:
+ case ATOMIC_WRITE:
+ case ATOMIC_RMW: {
+ ModelAction *ret = NULL;
+
+ /* linear search: from most recent to oldest */
+ action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
action_list_t::reverse_iterator rit;
- ModelAction *lastact = NULL;
-
- /* Find last action that happens after curr */
for (rit = list->rbegin(); rit != list->rend(); rit++) {
- ModelAction *act = *rit;
- if (curr->happens_before(act)) {
- lastact = act;
- } else
+ ModelAction *prev = *rit;
+ if (prev->could_synchronize_with(act)) {
+ ret = prev;
break;
+ }
}
- /* Include at most one act per-thread that "happens before" curr */
- if (lastact != NULL) {
- if (lastact->is_read()) {
- const ModelAction *postreadfrom = lastact->get_reads_from();
- if (postreadfrom != NULL&&rf != postreadfrom)
- mo_graph->addEdge(rf, postreadfrom);
- } else if (rf != lastact) {
- mo_graph->addEdge(rf, lastact);
- }
- break;
+ ModelAction *ret2 = get_last_fence_conflict(act);
+ if (!ret2)
+ return ret;
+ if (!ret)
+ return ret2;
+ if (*ret < *ret2)
+ return ret2;
+ return ret;
+ }
+ case ATOMIC_LOCK:
+ case ATOMIC_TRYLOCK: {
+ /* linear search: from most recent to oldest */
+ action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *prev = *rit;
+ if (act->is_conflicting_lock(prev))
+ return prev;
+ }
+ break;
+ }
+ case ATOMIC_UNLOCK: {
+ /* linear search: from most recent to oldest */
+ action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *prev = *rit;
+ if (!act->same_thread(prev) && prev->is_failed_trylock())
+ return prev;
+ }
+ break;
+ }
+ case ATOMIC_WAIT: {
+ /* linear search: from most recent to oldest */
+ action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *prev = *rit;
+ if (!act->same_thread(prev) && prev->is_failed_trylock())
+ return prev;
+ if (!act->same_thread(prev) && prev->is_notify())
+ return prev;
+ }
+ break;
+ }
+
+ case ATOMIC_NOTIFY_ALL:
+ case ATOMIC_NOTIFY_ONE: {
+ /* linear search: from most recent to oldest */
+ action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *prev = *rit;
+ if (!act->same_thread(prev) && prev->is_wait())
+ return prev;
}
+ break;
}
+ default:
+ break;
+ }
+ return NULL;
+}
+
+/** This method finds backtracking points where we should try to
+ * reorder the parameter ModelAction against.
+ *
+ * @param the ModelAction to find backtracking points for.
+ */
+void ModelChecker::set_backtracking(ModelAction *act)
+{
+ Thread *t = get_thread(act);
+ ModelAction *prev = get_last_conflict(act);
+ if (prev == NULL)
+ return;
+
+ Node *node = prev->get_node()->get_parent();
+
+ int low_tid, high_tid;
+ if (node->enabled_status(t->get_id()) == THREAD_ENABLED) {
+ low_tid = id_to_int(act->get_tid());
+ high_tid = low_tid + 1;
+ } else {
+ low_tid = 0;
+ high_tid = get_num_threads();
+ }
+
+ for (int i = low_tid; i < high_tid; i++) {
+ thread_id_t tid = int_to_id(i);
+
+ /* Make sure this thread can be enabled here. */
+ if (i >= node->get_num_threads())
+ break;
+
+ /* Don't backtrack into a point where the thread is disabled or sleeping. */
+ if (node->enabled_status(tid) != THREAD_ENABLED)
+ continue;
+
+ /* Check if this has been explored already */
+ if (node->has_been_explored(tid))
+ continue;
+
+ /* See if fairness allows */
+ if (model->params.fairwindow != 0 && !node->has_priority(tid)) {
+ bool unfair = false;
+ for (int t = 0; t < node->get_num_threads(); t++) {
+ thread_id_t tother = int_to_id(t);
+ if (node->is_enabled(tother) && node->has_priority(tother)) {
+ unfair = true;
+ break;
+ }
+ }
+ if (unfair)
+ continue;
+ }
+ /* Cache the latest backtracking point */
+ set_latest_backtrack(prev);
+
+ /* If this is a new backtracking point, mark the tree */
+ if (!node->set_backtrack(tid))
+ continue;
+ DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
+ id_to_int(prev->get_tid()),
+ id_to_int(t->get_id()));
+ if (DBG_ENABLED()) {
+ prev->print();
+ act->print();
+ }
+ }
+}
+
+/**
+ * @brief Cache the a backtracking point as the "most recent", if eligible
+ *
+ * Note that this does not prepare the NodeStack for this backtracking
+ * operation, it only caches the action on a per-execution basis
+ *
+ * @param act The operation at which we should explore a different next action
+ * (i.e., backtracking point)
+ * @return True, if this action is now the most recent backtracking point;
+ * false otherwise
+ */
+bool ModelChecker::set_latest_backtrack(ModelAction *act)
+{
+ if (!priv->next_backtrack || *act > *priv->next_backtrack) {
+ priv->next_backtrack = act;
+ return true;
+ }
+ return false;
+}
+
+/**
+ * Returns last backtracking point. The model checker will explore a different
+ * path for this point in the next execution.
+ * @return The ModelAction at which the next execution should diverge.
+ */
+ModelAction * ModelChecker::get_next_backtrack()
+{
+ ModelAction *next = priv->next_backtrack;
+ priv->next_backtrack = NULL;
+ return next;
+}
+
+/**
+ * Processes a read or rmw model action.
+ * @param curr is the read model action to process.
+ * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw.
+ * @return True if processing this read updates the mo_graph.
+ */
+bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw)
+{
+ uint64_t value = VALUE_NONE;
+ bool updated = false;
+ while (true) {
+ const ModelAction *reads_from = curr->get_node()->get_read_from();
+ if (reads_from != NULL) {
+ mo_graph->startChanges();
+
+ value = reads_from->get_value();
+ bool r_status = false;
+
+ if (!second_part_of_rmw) {
+ check_recency(curr, reads_from);
+ r_status = r_modification_order(curr, reads_from);
+ }
+
+ if (!second_part_of_rmw && is_infeasible() && (curr->get_node()->increment_read_from() || curr->get_node()->increment_future_value())) {
+ mo_graph->rollbackChanges();
+ priv->too_many_reads = false;
+ continue;
+ }
+
+ read_from(curr, reads_from);
+ mo_graph->commitChanges();
+ mo_check_promises(curr, true);
+
+ updated |= r_status;
+ } else if (!second_part_of_rmw) {
+ /* Read from future value */
+ struct future_value fv = curr->get_node()->get_future_value();
+ Promise *promise = new Promise(curr, fv);
+ value = fv.value;
+ curr->set_read_from_promise(promise);
+ promises->push_back(promise);
+ mo_graph->startChanges();
+ updated = r_modification_order(curr, promise);
+ mo_graph->commitChanges();
+ }
+ get_thread(curr)->set_return_value(value);
+ return updated;
+ }
+}
+
+/**
+ * Processes a lock, trylock, or unlock model action. @param curr is
+ * the read model action to process.
+ *
+ * The try lock operation checks whether the lock is taken. If not,
+ * it falls to the normal lock operation case. If so, it returns
+ * fail.
+ *
+ * The lock operation has already been checked that it is enabled, so
+ * it just grabs the lock and synchronizes with the previous unlock.
+ *
+ * The unlock operation has to re-enable all of the threads that are
+ * waiting on the lock.
+ *
+ * @return True if synchronization was updated; false otherwise
+ */
+bool ModelChecker::process_mutex(ModelAction *curr)
+{
+ std::mutex *mutex = NULL;
+ struct std::mutex_state *state = NULL;
+
+ if (curr->is_trylock() || curr->is_lock() || curr->is_unlock()) {
+ mutex = (std::mutex *)curr->get_location();
+ state = mutex->get_state();
+ } else if (curr->is_wait()) {
+ mutex = (std::mutex *)curr->get_value();
+ state = mutex->get_state();
+ }
+
+ switch (curr->get_type()) {
+ case ATOMIC_TRYLOCK: {
+ bool success = !state->islocked;
+ curr->set_try_lock(success);
+ if (!success) {
+ get_thread(curr)->set_return_value(0);
+ break;
+ }
+ get_thread(curr)->set_return_value(1);
+ }
+ //otherwise fall into the lock case
+ case ATOMIC_LOCK: {
+ if (curr->get_cv()->getClock(state->alloc_tid) <= state->alloc_clock)
+ assert_bug("Lock access before initialization");
+ state->islocked = true;
+ ModelAction *unlock = get_last_unlock(curr);
+ //synchronize with the previous unlock statement
+ if (unlock != NULL) {
+ curr->synchronize_with(unlock);
+ return true;
+ }
+ break;
+ }
+ case ATOMIC_UNLOCK: {
+ //unlock the lock
+ state->islocked = false;
+ //wake up the other threads
+ action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, curr->get_location());
+ //activate all the waiting threads
+ for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
+ scheduler->wake(get_thread(*rit));
+ }
+ waiters->clear();
+ break;
+ }
+ case ATOMIC_WAIT: {
+ //unlock the lock
+ state->islocked = false;
+ //wake up the other threads
+ action_list_t *waiters = get_safe_ptr_action(lock_waiters_map, (void *) curr->get_value());
+ //activate all the waiting threads
+ for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
+ scheduler->wake(get_thread(*rit));
+ }
+ waiters->clear();
+ //check whether we should go to sleep or not...simulate spurious failures
+ if (curr->get_node()->get_misc() == 0) {
+ get_safe_ptr_action(condvar_waiters_map, curr->get_location())->push_back(curr);
+ //disable us
+ scheduler->sleep(get_thread(curr));
+ }
+ break;
+ }
+ case ATOMIC_NOTIFY_ALL: {
+ action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
+ //activate all the waiting threads
+ for (action_list_t::iterator rit = waiters->begin(); rit != waiters->end(); rit++) {
+ scheduler->wake(get_thread(*rit));
+ }
+ waiters->clear();
+ break;
+ }
+ case ATOMIC_NOTIFY_ONE: {
+ action_list_t *waiters = get_safe_ptr_action(condvar_waiters_map, curr->get_location());
+ int wakeupthread = curr->get_node()->get_misc();
+ action_list_t::iterator it = waiters->begin();
+ advance(it, wakeupthread);
+ scheduler->wake(get_thread(*it));
+ waiters->erase(it);
+ break;
+ }
+
+ default:
+ ASSERT(0);
+ }
+ return false;
+}
+
+void ModelChecker::add_future_value(const ModelAction *writer, ModelAction *reader)
+{
+ /* Do more ambitious checks now that mo is more complete */
+ if (mo_may_allow(writer, reader)) {
+ Node *node = reader->get_node();
+
+ /* Find an ancestor thread which exists at the time of the reader */
+ Thread *write_thread = get_thread(writer);
+ while (id_to_int(write_thread->get_id()) >= node->get_num_threads())
+ write_thread = write_thread->get_parent();
+
+ struct future_value fv = {
+ writer->get_value(),
+ writer->get_seq_number() + params.maxfuturedelay,
+ write_thread->get_id(),
+ };
+ if (node->add_future_value(fv))
+ set_latest_backtrack(reader);
+ }
+}
+
+/**
+ * Process a write ModelAction
+ * @param curr The ModelAction to process
+ * @return True if the mo_graph was updated or promises were resolved
+ */
+bool ModelChecker::process_write(ModelAction *curr)
+{
+ bool updated_mod_order = w_modification_order(curr);
+ bool updated_promises = resolve_promises(curr);
+
+ if (promises->size() == 0) {
+ for (unsigned int i = 0; i < futurevalues->size(); i++) {
+ struct PendingFutureValue pfv = (*futurevalues)[i];
+ add_future_value(pfv.writer, pfv.act);
+ }
+ futurevalues->clear();
+ }
+
+ mo_graph->commitChanges();
+ mo_check_promises(curr, false);
+
+ get_thread(curr)->set_return_value(VALUE_NONE);
+ return updated_mod_order || updated_promises;
+}
+
+/**
+ * Process a fence ModelAction
+ * @param curr The ModelAction to process
+ * @return True if synchronization was updated
+ */
+bool ModelChecker::process_fence(ModelAction *curr)
+{
+ /*
+ * fence-relaxed: no-op
+ * fence-release: only log the occurence (not in this function), for
+ * use in later synchronization
+ * fence-acquire (this function): search for hypothetical release
+ * sequences
+ */
+ bool updated = false;
+ if (curr->is_acquire()) {
+ action_list_t *list = action_trace;
+ action_list_t::reverse_iterator rit;
+ /* Find X : is_read(X) && X --sb-> curr */
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *act = *rit;
+ if (act == curr)
+ continue;
+ if (act->get_tid() != curr->get_tid())
+ continue;
+ /* Stop at the beginning of the thread */
+ if (act->is_thread_start())
+ break;
+ /* Stop once we reach a prior fence-acquire */
+ if (act->is_fence() && act->is_acquire())
+ break;
+ if (!act->is_read())
+ continue;
+ /* read-acquire will find its own release sequences */
+ if (act->is_acquire())
+ continue;
+
+ /* Establish hypothetical release sequences */
+ rel_heads_list_t release_heads;
+ get_release_seq_heads(curr, act, &release_heads);
+ for (unsigned int i = 0; i < release_heads.size(); i++)
+ if (!curr->synchronize_with(release_heads[i]))
+ set_bad_synchronization();
+ if (release_heads.size() != 0)
+ updated = true;
+ }
+ }
+ return updated;
+}
+
+/**
+ * @brief Process the current action for thread-related activity
+ *
+ * Performs current-action processing for a THREAD_* ModelAction. Proccesses
+ * may include setting Thread status, completing THREAD_FINISH/THREAD_JOIN
+ * synchronization, etc. This function is a no-op for non-THREAD actions
+ * (e.g., ATOMIC_{READ,WRITE,RMW,LOCK}, etc.)
+ *
+ * @param curr The current action
+ * @return True if synchronization was updated or a thread completed
+ */
+bool ModelChecker::process_thread_action(ModelAction *curr)
+{
+ bool updated = false;
+
+ switch (curr->get_type()) {
+ case THREAD_CREATE: {
+ thrd_t *thrd = (thrd_t *)curr->get_location();
+ struct thread_params *params = (struct thread_params *)curr->get_value();
+ Thread *th = new Thread(thrd, params->func, params->arg, get_thread(curr));
+ add_thread(th);
+ th->set_creation(curr);
+ /* Promises can be satisfied by children */
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ if (promise->thread_is_available(curr->get_tid()))
+ promise->add_thread(th->get_id());
+ }
+ break;
+ }
+ case THREAD_JOIN: {
+ Thread *blocking = curr->get_thread_operand();
+ ModelAction *act = get_last_action(blocking->get_id());
+ curr->synchronize_with(act);
+ updated = true; /* trigger rel-seq checks */
+ break;
+ }
+ case THREAD_FINISH: {
+ Thread *th = get_thread(curr);
+ while (!th->wait_list_empty()) {
+ ModelAction *act = th->pop_wait_list();
+ scheduler->wake(get_thread(act));
+ }
+ th->complete();
+ /* Completed thread can't satisfy promises */
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ if (promise->thread_is_available(th->get_id()))
+ if (promise->eliminate_thread(th->get_id()))
+ priv->failed_promise = true;
+ }
+ updated = true; /* trigger rel-seq checks */
+ break;
+ }
+ case THREAD_START: {
+ check_promises(curr->get_tid(), NULL, curr->get_cv());
+ break;
+ }
+ default:
+ break;
+ }
+
+ return updated;
+}
+
+/**
+ * @brief Process the current action for release sequence fixup activity
+ *
+ * Performs model-checker release sequence fixups for the current action,
+ * forcing a single pending release sequence to break (with a given, potential
+ * "loose" write) or to complete (i.e., synchronize). If a pending release
+ * sequence forms a complete release sequence, then we must perform the fixup
+ * synchronization, mo_graph additions, etc.
+ *
+ * @param curr The current action; must be a release sequence fixup action
+ * @param work_queue The work queue to which to add work items as they are
+ * generated
+ */
+void ModelChecker::process_relseq_fixup(ModelAction *curr, work_queue_t *work_queue)
+{
+ const ModelAction *write = curr->get_node()->get_relseq_break();
+ struct release_seq *sequence = pending_rel_seqs->back();
+ pending_rel_seqs->pop_back();
+ ASSERT(sequence);
+ ModelAction *acquire = sequence->acquire;
+ const ModelAction *rf = sequence->rf;
+ const ModelAction *release = sequence->release;
+ ASSERT(acquire);
+ ASSERT(release);
+ ASSERT(rf);
+ ASSERT(release->same_thread(rf));
+
+ if (write == NULL) {
+ /**
+ * @todo Forcing a synchronization requires that we set
+ * modification order constraints. For instance, we can't allow
+ * a fixup sequence in which two separate read-acquire
+ * operations read from the same sequence, where the first one
+ * synchronizes and the other doesn't. Essentially, we can't
+ * allow any writes to insert themselves between 'release' and
+ * 'rf'
+ */
+
+ /* Must synchronize */
+ if (!acquire->synchronize_with(release)) {
+ set_bad_synchronization();
+ return;
+ }
+ /* Re-check all pending release sequences */
+ work_queue->push_back(CheckRelSeqWorkEntry(NULL));
+ /* Re-check act for mo_graph edges */
+ work_queue->push_back(MOEdgeWorkEntry(acquire));
+
+ /* propagate synchronization to later actions */
+ action_list_t::reverse_iterator rit = action_trace->rbegin();
+ for (; (*rit) != acquire; rit++) {
+ ModelAction *propagate = *rit;
+ if (acquire->happens_before(propagate)) {
+ propagate->synchronize_with(acquire);
+ /* Re-check 'propagate' for mo_graph edges */
+ work_queue->push_back(MOEdgeWorkEntry(propagate));
+ }
+ }
+ } else {
+ /* Break release sequence with new edges:
+ * release --mo--> write --mo--> rf */
+ mo_graph->addEdge(release, write);
+ mo_graph->addEdge(write, rf);
+ }
+
+ /* See if we have realized a data race */
+ checkDataRaces();
+}
+
+/**
+ * Initialize the current action by performing one or more of the following
+ * actions, as appropriate: merging RMWR and RMWC/RMW actions, stepping forward
+ * in the NodeStack, manipulating backtracking sets, allocating and
+ * initializing clock vectors, and computing the promises to fulfill.
+ *
+ * @param curr The current action, as passed from the user context; may be
+ * freed/invalidated after the execution of this function, with a different
+ * action "returned" its place (pass-by-reference)
+ * @return True if curr is a newly-explored action; false otherwise
+ */
+bool ModelChecker::initialize_curr_action(ModelAction **curr)
+{
+ ModelAction *newcurr;
+
+ if ((*curr)->is_rmwc() || (*curr)->is_rmw()) {
+ newcurr = process_rmw(*curr);
+ delete *curr;
+
+ if (newcurr->is_rmw())
+ compute_promises(newcurr);
+
+ *curr = newcurr;
+ return false;
+ }
+
+ (*curr)->set_seq_number(get_next_seq_num());
+
+ newcurr = node_stack->explore_action(*curr, scheduler->get_enabled_array());
+ if (newcurr) {
+ /* First restore type and order in case of RMW operation */
+ if ((*curr)->is_rmwr())
+ newcurr->copy_typeandorder(*curr);
+
+ ASSERT((*curr)->get_location() == newcurr->get_location());
+ newcurr->copy_from_new(*curr);
+
+ /* Discard duplicate ModelAction; use action from NodeStack */
+ delete *curr;
+
+ /* Always compute new clock vector */
+ newcurr->create_cv(get_parent_action(newcurr->get_tid()));
+
+ *curr = newcurr;
+ return false; /* Action was explored previously */
+ } else {
+ newcurr = *curr;
+
+ /* Always compute new clock vector */
+ newcurr->create_cv(get_parent_action(newcurr->get_tid()));
+
+ /* Assign most recent release fence */
+ newcurr->set_last_fence_release(get_last_fence_release(newcurr->get_tid()));
+
+ /*
+ * Perform one-time actions when pushing new ModelAction onto
+ * NodeStack
+ */
+ if (newcurr->is_write())
+ compute_promises(newcurr);
+ else if (newcurr->is_relseq_fixup())
+ compute_relseq_breakwrites(newcurr);
+ else if (newcurr->is_wait())
+ newcurr->get_node()->set_misc_max(2);
+ else if (newcurr->is_notify_one()) {
+ newcurr->get_node()->set_misc_max(get_safe_ptr_action(condvar_waiters_map, newcurr->get_location())->size());
+ }
+ return true; /* This was a new ModelAction */
+ }
+}
+
+/**
+ * @brief Establish reads-from relation between two actions
+ *
+ * Perform basic operations involved with establishing a concrete rf relation,
+ * including setting the ModelAction data and checking for release sequences.
+ *
+ * @param act The action that is reading (must be a read)
+ * @param rf The action from which we are reading (must be a write)
+ *
+ * @return True if this read established synchronization
+ */
+bool ModelChecker::read_from(ModelAction *act, const ModelAction *rf)
+{
+ act->set_read_from(rf);
+ if (rf != NULL && act->is_acquire()) {
+ rel_heads_list_t release_heads;
+ get_release_seq_heads(act, act, &release_heads);
+ int num_heads = release_heads.size();
+ for (unsigned int i = 0; i < release_heads.size(); i++)
+ if (!act->synchronize_with(release_heads[i])) {
+ set_bad_synchronization();
+ num_heads--;
+ }
+ return num_heads > 0;
+ }
+ return false;
+}
+
+/**
+ * @brief Check whether a model action is enabled.
+ *
+ * Checks whether a lock or join operation would be successful (i.e., is the
+ * lock already locked, or is the joined thread already complete). If not, put
+ * the action in a waiter list.
+ *
+ * @param curr is the ModelAction to check whether it is enabled.
+ * @return a bool that indicates whether the action is enabled.
+ */
+bool ModelChecker::check_action_enabled(ModelAction *curr) {
+ if (curr->is_lock()) {
+ std::mutex *lock = (std::mutex *)curr->get_location();
+ struct std::mutex_state *state = lock->get_state();
+ if (state->islocked) {
+ //Stick the action in the appropriate waiting queue
+ get_safe_ptr_action(lock_waiters_map, curr->get_location())->push_back(curr);
+ return false;
+ }
+ } else if (curr->get_type() == THREAD_JOIN) {
+ Thread *blocking = (Thread *)curr->get_location();
+ if (!blocking->is_complete()) {
+ blocking->push_wait_list(curr);
+ return false;
+ }
+ }
+
+ return true;
+}
+
+/**
+ * This is the heart of the model checker routine. It performs model-checking
+ * actions corresponding to a given "current action." Among other processes, it
+ * calculates reads-from relationships, updates synchronization clock vectors,
+ * forms a memory_order constraints graph, and handles replay/backtrack
+ * execution when running permutations of previously-observed executions.
+ *
+ * @param curr The current action to process
+ * @return The ModelAction that is actually executed; may be different than
+ * curr; may be NULL, if the current action is not enabled to run
+ */
+ModelAction * ModelChecker::check_current_action(ModelAction *curr)
+{
+ ASSERT(curr);
+ bool second_part_of_rmw = curr->is_rmwc() || curr->is_rmw();
+
+ if (!check_action_enabled(curr)) {
+ /* Make the execution look like we chose to run this action
+ * much later, when a lock/join can succeed */
+ get_thread(curr)->set_pending(curr);
+ scheduler->sleep(get_thread(curr));
+ return NULL;
+ }
+
+ bool newly_explored = initialize_curr_action(&curr);
+
+ DBG();
+ if (DBG_ENABLED())
+ curr->print();
+
+ wake_up_sleeping_actions(curr);
+
+ /* Add the action to lists before any other model-checking tasks */
+ if (!second_part_of_rmw)
+ add_action_to_lists(curr);
+
+ /* Build may_read_from set for newly-created actions */
+ if (newly_explored && curr->is_read())
+ build_may_read_from(curr);
+
+ /* Initialize work_queue with the "current action" work */
+ work_queue_t work_queue(1, CheckCurrWorkEntry(curr));
+ while (!work_queue.empty() && !has_asserted()) {
+ WorkQueueEntry work = work_queue.front();
+ work_queue.pop_front();
+
+ switch (work.type) {
+ case WORK_CHECK_CURR_ACTION: {
+ ModelAction *act = work.action;
+ bool update = false; /* update this location's release seq's */
+ bool update_all = false; /* update all release seq's */
+
+ if (process_thread_action(curr))
+ update_all = true;
+
+ if (act->is_read() && process_read(act, second_part_of_rmw))
+ update = true;
+
+ if (act->is_write() && process_write(act))
+ update = true;
+
+ if (act->is_fence() && process_fence(act))
+ update_all = true;
+
+ if (act->is_mutex_op() && process_mutex(act))
+ update_all = true;
+
+ if (act->is_relseq_fixup())
+ process_relseq_fixup(curr, &work_queue);
+
+ if (update_all)
+ work_queue.push_back(CheckRelSeqWorkEntry(NULL));
+ else if (update)
+ work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
+ break;
+ }
+ case WORK_CHECK_RELEASE_SEQ:
+ resolve_release_sequences(work.location, &work_queue);
+ break;
+ case WORK_CHECK_MO_EDGES: {
+ /** @todo Complete verification of work_queue */
+ ModelAction *act = work.action;
+ bool updated = false;
+
+ if (act->is_read()) {
+ const ModelAction *rf = act->get_reads_from();
+ const Promise *promise = act->get_reads_from_promise();
+ if (rf) {
+ if (r_modification_order(act, rf))
+ updated = true;
+ } else if (promise) {
+ if (r_modification_order(act, promise))
+ updated = true;
+ }
+ }
+ if (act->is_write()) {
+ if (w_modification_order(act))
+ updated = true;
+ }
+ mo_graph->commitChanges();
+
+ if (updated)
+ work_queue.push_back(CheckRelSeqWorkEntry(act->get_location()));
+ break;
+ }
+ default:
+ ASSERT(false);
+ break;
+ }
+ }
+
+ check_curr_backtracking(curr);
+ set_backtracking(curr);
+ return curr;
+}
+
+void ModelChecker::check_curr_backtracking(ModelAction *curr)
+{
+ Node *currnode = curr->get_node();
+ Node *parnode = currnode->get_parent();
+
+ if ((parnode && !parnode->backtrack_empty()) ||
+ !currnode->misc_empty() ||
+ !currnode->read_from_empty() ||
+ !currnode->future_value_empty() ||
+ !currnode->promise_empty() ||
+ !currnode->relseq_break_empty()) {
+ set_latest_backtrack(curr);
+ }
+}
+
+bool ModelChecker::promises_expired() const
+{
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ if (promise->get_expiration() < priv->used_sequence_numbers)
+ return true;
+ }
+ return false;
+}
+
+/**
+ * This is the strongest feasibility check available.
+ * @return whether the current trace (partial or complete) must be a prefix of
+ * a feasible trace.
+ */
+bool ModelChecker::isfeasibleprefix() const
+{
+ return pending_rel_seqs->size() == 0 && is_feasible_prefix_ignore_relseq();
+}
+
+/**
+ * Print disagnostic information about an infeasible execution
+ * @param prefix A string to prefix the output with; if NULL, then a default
+ * message prefix will be provided
+ */
+void ModelChecker::print_infeasibility(const char *prefix) const
+{
+ char buf[100];
+ char *ptr = buf;
+ if (mo_graph->checkForCycles())
+ ptr += sprintf(ptr, "[mo cycle]");
+ if (priv->failed_promise)
+ ptr += sprintf(ptr, "[failed promise]");
+ if (priv->too_many_reads)
+ ptr += sprintf(ptr, "[too many reads]");
+ if (priv->no_valid_reads)
+ ptr += sprintf(ptr, "[no valid reads-from]");
+ if (priv->bad_synchronization)
+ ptr += sprintf(ptr, "[bad sw ordering]");
+ if (promises_expired())
+ ptr += sprintf(ptr, "[promise expired]");
+ if (promises->size() != 0)
+ ptr += sprintf(ptr, "[unresolved promise]");
+ if (ptr != buf)
+ model_print("%s: %s\n", prefix ? prefix : "Infeasible", buf);
+}
+
+/**
+ * Returns whether the current completed trace is feasible, except for pending
+ * release sequences.
+ */
+bool ModelChecker::is_feasible_prefix_ignore_relseq() const
+{
+ return !is_infeasible() && promises->size() == 0;
+}
+
+/**
+ * Check if the current partial trace is infeasible. Does not check any
+ * end-of-execution flags, which might rule out the execution. Thus, this is
+ * useful only for ruling an execution as infeasible.
+ * @return whether the current partial trace is infeasible.
+ */
+bool ModelChecker::is_infeasible() const
+{
+ return mo_graph->checkForCycles() ||
+ priv->no_valid_reads ||
+ priv->failed_promise ||
+ priv->too_many_reads ||
+ priv->bad_synchronization ||
+ promises_expired();
+}
+
+/** Close out a RMWR by converting previous RMWR into a RMW or READ. */
+ModelAction * ModelChecker::process_rmw(ModelAction *act) {
+ ModelAction *lastread = get_last_action(act->get_tid());
+ lastread->process_rmw(act);
+ if (act->is_rmw()) {
+ if (lastread->get_reads_from())
+ mo_graph->addRMWEdge(lastread->get_reads_from(), lastread);
+ else
+ mo_graph->addRMWEdge(lastread->get_reads_from_promise(), lastread);
+ mo_graph->commitChanges();
+ }
+ return lastread;
+}
+
+/**
+ * Checks whether a thread has read from the same write for too many times
+ * without seeing the effects of a later write.
+ *
+ * Basic idea:
+ * 1) there must a different write that we could read from that would satisfy the modification order,
+ * 2) we must have read from the same value in excess of maxreads times, and
+ * 3) that other write must have been in the reads_from set for maxreads times.
+ *
+ * If so, we decide that the execution is no longer feasible.
+ */
+void ModelChecker::check_recency(ModelAction *curr, const ModelAction *rf)
+{
+ if (params.maxreads != 0) {
+ if (curr->get_node()->get_read_from_size() <= 1)
+ return;
+ //Must make sure that execution is currently feasible... We could
+ //accidentally clear by rolling back
+ if (is_infeasible())
+ return;
+ std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
+ int tid = id_to_int(curr->get_tid());
+
+ /* Skip checks */
+ if ((int)thrd_lists->size() <= tid)
+ return;
+ action_list_t *list = &(*thrd_lists)[tid];
+
+ action_list_t::reverse_iterator rit = list->rbegin();
+ /* Skip past curr */
+ for (; (*rit) != curr; rit++)
+ ;
+ /* go past curr now */
+ rit++;
+
+ action_list_t::reverse_iterator ritcopy = rit;
+ //See if we have enough reads from the same value
+ int count = 0;
+ for (; count < params.maxreads; rit++, count++) {
+ if (rit == list->rend())
+ return;
+ ModelAction *act = *rit;
+ if (!act->is_read())
+ return;
+
+ if (act->get_reads_from() != rf)
+ return;
+ if (act->get_node()->get_read_from_size() <= 1)
+ return;
+ }
+ for (int i = 0; i < curr->get_node()->get_read_from_size(); i++) {
+ /* Get write */
+ const ModelAction *write = curr->get_node()->get_read_from_at(i);
+
+ /* Need a different write */
+ if (write == rf)
+ continue;
+
+ /* Test to see whether this is a feasible write to read from */
+ /** NOTE: all members of read-from set should be
+ * feasible, so we no longer check it here **/
+
+ rit = ritcopy;
+
+ bool feasiblewrite = true;
+ //new we need to see if this write works for everyone
+
+ for (int loop = count; loop > 0; loop--, rit++) {
+ ModelAction *act = *rit;
+ bool foundvalue = false;
+ for (int j = 0; j < act->get_node()->get_read_from_size(); j++) {
+ if (act->get_node()->get_read_from_at(j) == write) {
+ foundvalue = true;
+ break;
+ }
+ }
+ if (!foundvalue) {
+ feasiblewrite = false;
+ break;
+ }
+ }
+ if (feasiblewrite) {
+ priv->too_many_reads = true;
+ return;
+ }
+ }
+ }
+}
+
+/**
+ * Updates the mo_graph with the constraints imposed from the current
+ * read.
+ *
+ * Basic idea is the following: Go through each other thread and find
+ * the last action that happened before our read. Two cases:
+ *
+ * (1) The action is a write => that write must either occur before
+ * the write we read from or be the write we read from.
+ *
+ * (2) The action is a read => the write that that action read from
+ * must occur before the write we read from or be the same write.
+ *
+ * @param curr The current action. Must be a read.
+ * @param rf The ModelAction or Promise that curr reads from. Must be a write.
+ * @return True if modification order edges were added; false otherwise
+ */
+template <typename rf_type>
+bool ModelChecker::r_modification_order(ModelAction *curr, const rf_type *rf)
+{
+ std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
+ unsigned int i;
+ bool added = false;
+ ASSERT(curr->is_read());
+
+ /* Last SC fence in the current thread */
+ ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
+
+ /* Iterate over all threads */
+ for (i = 0; i < thrd_lists->size(); i++) {
+ /* Last SC fence in thread i */
+ ModelAction *last_sc_fence_thread_local = NULL;
+ if (int_to_id((int)i) != curr->get_tid())
+ last_sc_fence_thread_local = get_last_seq_cst_fence(int_to_id(i), NULL);
+
+ /* Last SC fence in thread i, before last SC fence in current thread */
+ ModelAction *last_sc_fence_thread_before = NULL;
+ if (last_sc_fence_local)
+ last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
+
+ /* Iterate over actions in thread, starting from most recent */
+ action_list_t *list = &(*thrd_lists)[i];
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *act = *rit;
+
+ if (act->is_write() && !act->equals(rf) && act != curr) {
+ /* C++, Section 29.3 statement 5 */
+ if (curr->is_seqcst() && last_sc_fence_thread_local &&
+ *act < *last_sc_fence_thread_local) {
+ added = mo_graph->addEdge(act, rf) || added;
+ break;
+ }
+ /* C++, Section 29.3 statement 4 */
+ else if (act->is_seqcst() && last_sc_fence_local &&
+ *act < *last_sc_fence_local) {
+ added = mo_graph->addEdge(act, rf) || added;
+ break;
+ }
+ /* C++, Section 29.3 statement 6 */
+ else if (last_sc_fence_thread_before &&
+ *act < *last_sc_fence_thread_before) {
+ added = mo_graph->addEdge(act, rf) || added;
+ break;
+ }
+ }
+
+ /*
+ * Include at most one act per-thread that "happens
+ * before" curr. Don't consider reflexively.
+ */
+ if (act->happens_before(curr) && act != curr) {
+ if (act->is_write()) {
+ if (!act->equals(rf)) {
+ added = mo_graph->addEdge(act, rf) || added;
+ }
+ } else {
+ const ModelAction *prevreadfrom = act->get_reads_from();
+ //if the previous read is unresolved, keep going...
+ if (prevreadfrom == NULL)
+ continue;
+
+ if (!prevreadfrom->equals(rf)) {
+ added = mo_graph->addEdge(prevreadfrom, rf) || added;
+ }
+ }
+ break;
+ }
+ }
+ }
+
+ /*
+ * All compatible, thread-exclusive promises must be ordered after any
+ * concrete loads from the same thread
+ */
+ for (unsigned int i = 0; i < promises->size(); i++)
+ if ((*promises)[i]->is_compatible_exclusive(curr))
+ added = mo_graph->addEdge(rf, (*promises)[i]) || added;
+
+ return added;
+}
+
+/**
+ * Updates the mo_graph with the constraints imposed from the current write.
+ *
+ * Basic idea is the following: Go through each other thread and find
+ * the lastest action that happened before our write. Two cases:
+ *
+ * (1) The action is a write => that write must occur before
+ * the current write
+ *
+ * (2) The action is a read => the write that that action read from
+ * must occur before the current write.
+ *
+ * This method also handles two other issues:
+ *
+ * (I) Sequential Consistency: Making sure that if the current write is
+ * seq_cst, that it occurs after the previous seq_cst write.
+ *
+ * (II) Sending the write back to non-synchronizing reads.
+ *
+ * @param curr The current action. Must be a write.
+ * @return True if modification order edges were added; false otherwise
+ */
+bool ModelChecker::w_modification_order(ModelAction *curr)
+{
+ std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
+ unsigned int i;
+ bool added = false;
+ ASSERT(curr->is_write());
+
+ if (curr->is_seqcst()) {
+ /* We have to at least see the last sequentially consistent write,
+ so we are initialized. */
+ ModelAction *last_seq_cst = get_last_seq_cst_write(curr);
+ if (last_seq_cst != NULL) {
+ added = mo_graph->addEdge(last_seq_cst, curr) || added;
+ }
+ }
+
+ /* Last SC fence in the current thread */
+ ModelAction *last_sc_fence_local = get_last_seq_cst_fence(curr->get_tid(), NULL);
+
+ /* Iterate over all threads */
+ for (i = 0; i < thrd_lists->size(); i++) {
+ /* Last SC fence in thread i, before last SC fence in current thread */
+ ModelAction *last_sc_fence_thread_before = NULL;
+ if (last_sc_fence_local && int_to_id((int)i) != curr->get_tid())
+ last_sc_fence_thread_before = get_last_seq_cst_fence(int_to_id(i), last_sc_fence_local);
+
+ /* Iterate over actions in thread, starting from most recent */
+ action_list_t *list = &(*thrd_lists)[i];
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++) {
+ ModelAction *act = *rit;
+ if (act == curr) {
+ /*
+ * 1) If RMW and it actually read from something, then we
+ * already have all relevant edges, so just skip to next
+ * thread.
+ *
+ * 2) If RMW and it didn't read from anything, we should
+ * whatever edge we can get to speed up convergence.
+ *
+ * 3) If normal write, we need to look at earlier actions, so
+ * continue processing list.
+ */
+ if (curr->is_rmw()) {
+ if (curr->get_reads_from() != NULL)
+ break;
+ else
+ continue;
+ } else
+ continue;
+ }
+
+ /* C++, Section 29.3 statement 7 */
+ if (last_sc_fence_thread_before && act->is_write() &&
+ *act < *last_sc_fence_thread_before) {
+ added = mo_graph->addEdge(act, curr) || added;
+ break;
+ }
+
+ /*
+ * Include at most one act per-thread that "happens
+ * before" curr
+ */
+ if (act->happens_before(curr)) {
+ /*
+ * Note: if act is RMW, just add edge:
+ * act --mo--> curr
+ * The following edge should be handled elsewhere:
+ * readfrom(act) --mo--> act
+ */
+ if (act->is_write())
+ added = mo_graph->addEdge(act, curr) || added;
+ else if (act->is_read()) {
+ //if previous read accessed a null, just keep going
+ if (act->get_reads_from() == NULL)
+ continue;
+ added = mo_graph->addEdge(act->get_reads_from(), curr) || added;
+ }
+ break;
+ } else if (act->is_read() && !act->could_synchronize_with(curr) &&
+ !act->same_thread(curr)) {
+ /* We have an action that:
+ (1) did not happen before us
+ (2) is a read and we are a write
+ (3) cannot synchronize with us
+ (4) is in a different thread
+ =>
+ that read could potentially read from our write. Note that
+ these checks are overly conservative at this point, we'll
+ do more checks before actually removing the
+ pendingfuturevalue.
+
+ */
+ if (thin_air_constraint_may_allow(curr, act)) {
+ if (!is_infeasible())
+ futurevalues->push_back(PendingFutureValue(curr, act));
+ else if (curr->is_rmw() && act->is_rmw() && curr->get_reads_from() && curr->get_reads_from() == act->get_reads_from())
+ add_future_value(curr, act);
+ }
+ }
+ }
+ }
+
+ /*
+ * All compatible, thread-exclusive promises must be ordered after any
+ * concrete stores to the same thread, or else they can be merged with
+ * this store later
+ */
+ for (unsigned int i = 0; i < promises->size(); i++)
+ if ((*promises)[i]->is_compatible_exclusive(curr))
+ added = mo_graph->addEdge(curr, (*promises)[i]) || added;
+
+ return added;
+}
+
+/** Arbitrary reads from the future are not allowed. Section 29.3
+ * part 9 places some constraints. This method checks one result of constraint
+ * constraint. Others require compiler support. */
+bool ModelChecker::thin_air_constraint_may_allow(const ModelAction *writer, const ModelAction *reader)
+{
+ if (!writer->is_rmw())
+ return true;
+
+ if (!reader->is_rmw())
+ return true;
+
+ for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) {
+ if (search == reader)
+ return false;
+ if (search->get_tid() == reader->get_tid() &&
+ search->happens_before(reader))
+ break;
+ }
+
+ return true;
}
/**
- * Updates the mo_graph with the constraints imposed from the current write.
- * @param curr The current action. Must be a write.
- * @return True if modification order edges were added; false otherwise
+ * Arbitrary reads from the future are not allowed. Section 29.3 part 9 places
+ * some constraints. This method checks one the following constraint (others
+ * require compiler support):
+ *
+ * If X --hb-> Y --mo-> Z, then X should not read from Z.
*/
-bool ModelChecker::w_modification_order(ModelAction *curr)
+bool ModelChecker::mo_may_allow(const ModelAction *writer, const ModelAction *reader)
{
- std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
+ std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, reader->get_location());
unsigned int i;
- bool added = false;
- ASSERT(curr->is_write());
-
- if (curr->is_seqcst()) {
- /* We have to at least see the last sequentially consistent write,
- so we are initialized. */
- ModelAction *last_seq_cst = get_last_seq_cst(curr->get_location());
- if (last_seq_cst != NULL) {
- mo_graph->addEdge(last_seq_cst, curr);
- added = true;
- }
- }
-
/* Iterate over all threads */
for (i = 0; i < thrd_lists->size(); i++) {
+ const ModelAction *write_after_read = NULL;
+
/* Iterate over actions in thread, starting from most recent */
action_list_t *list = &(*thrd_lists)[i];
action_list_t::reverse_iterator rit;
for (rit = list->rbegin(); rit != list->rend(); rit++) {
ModelAction *act = *rit;
- /* Include at most one act per-thread that "happens before" curr */
- if (act->happens_before(curr)) {
- if (act->is_read())
- mo_graph->addEdge(act->get_reads_from(), curr);
- else
- mo_graph->addEdge(act, curr);
- added = true;
+ /* Don't disallow due to act == reader */
+ if (!reader->happens_before(act) || reader == act)
break;
- } else if (act->is_read() && !act->is_synchronizing(curr) &&
- !act->same_thread(curr)) {
- /* We have an action that:
- (1) did not happen before us
- (2) is a read and we are a write
- (3) cannot synchronize with us
- (4) is in a different thread
- =>
- that read could potentially read from our write.
- */
- if (act->get_node()->add_future_value(curr->get_value()) &&
- (!next_backtrack || *act > *next_backtrack))
- next_backtrack = act;
- }
+ else if (act->is_write())
+ write_after_read = act;
+ else if (act->is_read() && act->get_reads_from() != NULL)
+ write_after_read = act->get_reads_from();
}
- }
- return added;
+ if (write_after_read && write_after_read != writer && mo_graph->checkReachable(write_after_read, writer))
+ return false;
+ }
+ return true;
}
/**
* "returns" two pieces of data: a pass-by-reference vector of @a release_heads
* and a boolean representing certainty.
*
- * @todo Finish lazy updating, when promises are fulfilled in the future
* @param rf The action that might be part of a release sequence. Must be a
* write.
- * @param release_heads A pass-by-reference style return parameter. After
+ * @param release_heads A pass-by-reference style return parameter. After
* execution of this function, release_heads will contain the heads of all the
- * relevant release sequences, if any exists
+ * relevant release sequences, if any exists with certainty
+ * @param pending A pass-by-reference style return parameter which is only used
+ * when returning false (i.e., uncertain). Returns most information regarding
+ * an uncertain release sequence, including any write operations that might
+ * break the sequence.
* @return true, if the ModelChecker is certain that release_heads is complete;
* false otherwise
*/
-bool ModelChecker::release_seq_head(const ModelAction *rf,
- std::vector<const ModelAction *> *release_heads) const
+bool ModelChecker::release_seq_heads(const ModelAction *rf,
+ rel_heads_list_t *release_heads,
+ struct release_seq *pending) const
{
- ASSERT(rf->is_write());
+ /* Only check for release sequences if there are no cycles */
+ if (mo_graph->checkForCycles())
+ return false;
+
+ for ( ; rf != NULL; rf = rf->get_reads_from()) {
+ ASSERT(rf->is_write());
+
+ if (rf->is_release())
+ release_heads->push_back(rf);
+ else if (rf->get_last_fence_release())
+ release_heads->push_back(rf->get_last_fence_release());
+ if (!rf->is_rmw())
+ break; /* End of RMW chain */
+
+ /** @todo Need to be smarter here... In the linux lock
+ * example, this will run to the beginning of the program for
+ * every acquire. */
+ /** @todo The way to be smarter here is to keep going until 1
+ * thread has a release preceded by an acquire and you've seen
+ * both. */
+
+ /* acq_rel RMW is a sufficient stopping condition */
+ if (rf->is_acquire() && rf->is_release())
+ return true; /* complete */
+ };
if (!rf) {
/* read from future: need to settle this later */
+ pending->rf = NULL;
return false; /* incomplete */
}
- if (rf->is_release())
- release_heads->push_back(rf);
- if (rf->is_rmw()) {
- if (rf->is_acquire())
- return true; /* complete */
- return release_seq_head(rf->get_reads_from(), release_heads);
- }
+
if (rf->is_release())
return true; /* complete */
- /* else relaxed write; check modification order for contiguous subsequence
- * -> rf must be same thread as release */
+ /* else relaxed write
+ * - check for fence-release in the same thread (29.8, stmt. 3)
+ * - check modification order for contiguous subsequence
+ * -> rf must be same thread as release */
+
+ const ModelAction *fence_release = rf->get_last_fence_release();
+ /* Synchronize with a fence-release unconditionally; we don't need to
+ * find any more "contiguous subsequence..." for it */
+ if (fence_release)
+ release_heads->push_back(fence_release);
+
int tid = id_to_int(rf->get_tid());
- std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(rf->get_location());
+ std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, rf->get_location());
action_list_t *list = &(*thrd_lists)[tid];
action_list_t::const_reverse_iterator rit;
/* Find rf in the thread list */
- for (rit = list->rbegin(); rit != list->rend(); rit++)
- if (*rit == rf)
- break;
+ rit = std::find(list->rbegin(), list->rend(), rf);
+ ASSERT(rit != list->rend());
- /* Find the last write/release */
- for (; rit != list->rend(); rit++)
+ /* Find the last {write,fence}-release */
+ for (; rit != list->rend(); rit++) {
+ if (fence_release && *(*rit) < *fence_release)
+ break;
if ((*rit)->is_release())
break;
+ }
if (rit == list->rend()) {
/* No write-release in this thread */
return true; /* complete */
- }
+ } else if (fence_release && *(*rit) < *fence_release) {
+ /* The fence-release is more recent (and so, "stronger") than
+ * the most recent write-release */
+ return true; /* complete */
+ } /* else, need to establish contiguous release sequence */
ModelAction *release = *rit;
ASSERT(rf->same_thread(release));
+ pending->writes.clear();
+
bool certain = true;
for (unsigned int i = 0; i < thrd_lists->size(); i++) {
if (id_to_int(rf->get_tid()) == (int)i)
continue;
list = &(*thrd_lists)[i];
+
+ /* Can we ensure no future writes from this thread may break
+ * the release seq? */
+ bool future_ordered = false;
+
+ ModelAction *last = get_last_action(int_to_id(i));
+ Thread *th = get_thread(int_to_id(i));
+ if ((last && rf->happens_before(last)) ||
+ !is_enabled(th) ||
+ th->is_complete())
+ future_ordered = true;
+
+ ASSERT(!th->is_model_thread() || future_ordered);
+
for (rit = list->rbegin(); rit != list->rend(); rit++) {
const ModelAction *act = *rit;
- if (!act->is_write())
- continue;
/* Reach synchronization -> this thread is complete */
if (act->happens_before(release))
break;
- if (rf->happens_before(act))
+ if (rf->happens_before(act)) {
+ future_ordered = true;
+ continue;
+ }
+
+ /* Only non-RMW writes can break release sequences */
+ if (!act->is_write() || act->is_rmw())
continue;
/* Check modification order */
- if (mo_graph->checkReachable(rf, act))
+ if (mo_graph->checkReachable(rf, act)) {
/* rf --mo--> act */
+ future_ordered = true;
continue;
+ }
if (mo_graph->checkReachable(act, release))
/* act --mo--> release */
break;
/* release --mo-> act --mo--> rf */
return true; /* complete */
}
+ /* act may break release sequence */
+ pending->writes.push_back(act);
certain = false;
}
+ if (!future_ordered)
+ certain = false; /* This thread is uncertain */
}
- if (certain)
+ if (certain) {
release_heads->push_back(release);
+ pending->writes.clear();
+ } else {
+ pending->release = release;
+ pending->rf = rf;
+ }
return certain;
}
/**
- * A public interface for getting the release sequence head(s) with which a
+ * An interface for getting the release sequence head(s) with which a
* given ModelAction must synchronize. This function only returns a non-empty
* result when it can locate a release sequence head with certainty. Otherwise,
* it may mark the internal state of the ModelChecker so that it will handle
- * the release sequence at a later time, causing @a act to update its
+ * the release sequence at a later time, causing @a acquire to update its
* synchronization at some later point in execution.
- * @param act The 'acquire' action that may read from a release sequence
+ *
+ * @param acquire The 'acquire' action that may synchronize with a release
+ * sequence
+ * @param read The read action that may read from a release sequence; this may
+ * be the same as acquire, or else an earlier action in the same thread (i.e.,
+ * when 'acquire' is a fence-acquire)
* @param release_heads A pass-by-reference return parameter. Will be filled
* with the head(s) of the release sequence(s), if they exists with certainty.
- * @see ModelChecker::release_seq_head
+ * @see ModelChecker::release_seq_heads
+ */
+void ModelChecker::get_release_seq_heads(ModelAction *acquire,
+ ModelAction *read, rel_heads_list_t *release_heads)
+{
+ const ModelAction *rf = read->get_reads_from();
+ struct release_seq *sequence = (struct release_seq *)snapshot_calloc(1, sizeof(struct release_seq));
+ sequence->acquire = acquire;
+ sequence->read = read;
+
+ if (!release_seq_heads(rf, release_heads, sequence)) {
+ /* add act to 'lazy checking' list */
+ pending_rel_seqs->push_back(sequence);
+ } else {
+ snapshot_free(sequence);
+ }
+}
+
+/**
+ * Attempt to resolve all stashed operations that might synchronize with a
+ * release sequence for a given location. This implements the "lazy" portion of
+ * determining whether or not a release sequence was contiguous, since not all
+ * modification order information is present at the time an action occurs.
+ *
+ * @param location The location/object that should be checked for release
+ * sequence resolutions. A NULL value means to check all locations.
+ * @param work_queue The work queue to which to add work items as they are
+ * generated
+ * @return True if any updates occurred (new synchronization, new mo_graph
+ * edges)
*/
-void ModelChecker::get_release_seq_heads(ModelAction *act,
- std::vector<const ModelAction *> *release_heads)
+bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue)
{
- const ModelAction *rf = act->get_reads_from();
- bool complete;
- complete = release_seq_head(rf, release_heads);
- if (!complete) {
- /** @todo complete lazy checking */
+ bool updated = false;
+ std::vector< struct release_seq *, SnapshotAlloc<struct release_seq *> >::iterator it = pending_rel_seqs->begin();
+ while (it != pending_rel_seqs->end()) {
+ struct release_seq *pending = *it;
+ ModelAction *acquire = pending->acquire;
+ const ModelAction *read = pending->read;
+
+ /* Only resolve sequences on the given location, if provided */
+ if (location && read->get_location() != location) {
+ it++;
+ continue;
+ }
+
+ const ModelAction *rf = read->get_reads_from();
+ rel_heads_list_t release_heads;
+ bool complete;
+ complete = release_seq_heads(rf, &release_heads, pending);
+ for (unsigned int i = 0; i < release_heads.size(); i++) {
+ if (!acquire->has_synchronized_with(release_heads[i])) {
+ if (acquire->synchronize_with(release_heads[i]))
+ updated = true;
+ else
+ set_bad_synchronization();
+ }
+ }
+
+ if (updated) {
+ /* Re-check all pending release sequences */
+ work_queue->push_back(CheckRelSeqWorkEntry(NULL));
+ /* Re-check read-acquire for mo_graph edges */
+ if (acquire->is_read())
+ work_queue->push_back(MOEdgeWorkEntry(acquire));
+
+ /* propagate synchronization to later actions */
+ action_list_t::reverse_iterator rit = action_trace->rbegin();
+ for (; (*rit) != acquire; rit++) {
+ ModelAction *propagate = *rit;
+ if (acquire->happens_before(propagate)) {
+ propagate->synchronize_with(acquire);
+ /* Re-check 'propagate' for mo_graph edges */
+ work_queue->push_back(MOEdgeWorkEntry(propagate));
+ }
+ }
+ }
+ if (complete) {
+ it = pending_rel_seqs->erase(it);
+ snapshot_free(pending);
+ } else {
+ it++;
+ }
}
+
+ // If we resolved promises or data races, see if we have realized a data race.
+ checkDataRaces();
+
+ return updated;
}
/**
void ModelChecker::add_action_to_lists(ModelAction *act)
{
int tid = id_to_int(act->get_tid());
- action_trace->push_back(act);
+ ModelAction *uninit = NULL;
+ int uninit_id = -1;
+ action_list_t *list = get_safe_ptr_action(obj_map, act->get_location());
+ if (list->empty() && act->is_atomic_var()) {
+ uninit = new_uninitialized_action(act->get_location());
+ uninit_id = id_to_int(uninit->get_tid());
+ list->push_back(uninit);
+ }
+ list->push_back(act);
- obj_map->get_safe_ptr(act->get_location())->push_back(act);
+ action_trace->push_back(act);
+ if (uninit)
+ action_trace->push_front(uninit);
- std::vector<action_list_t> *vec = obj_thrd_map->get_safe_ptr(act->get_location());
+ std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, act->get_location());
if (tid >= (int)vec->size())
- vec->resize(next_thread_id);
+ vec->resize(priv->next_thread_id);
(*vec)[tid].push_back(act);
+ if (uninit)
+ (*vec)[uninit_id].push_front(uninit);
if ((int)thrd_last_action->size() <= tid)
thrd_last_action->resize(get_num_threads());
(*thrd_last_action)[tid] = act;
+ if (uninit)
+ (*thrd_last_action)[uninit_id] = uninit;
+
+ if (act->is_fence() && act->is_release()) {
+ if ((int)thrd_last_fence_release->size() <= tid)
+ thrd_last_fence_release->resize(get_num_threads());
+ (*thrd_last_fence_release)[tid] = act;
+ }
+
+ if (act->is_wait()) {
+ void *mutex_loc = (void *) act->get_value();
+ get_safe_ptr_action(obj_map, mutex_loc)->push_back(act);
+
+ std::vector<action_list_t> *vec = get_safe_ptr_vect_action(obj_thrd_map, mutex_loc);
+ if (tid >= (int)vec->size())
+ vec->resize(priv->next_thread_id);
+ (*vec)[tid].push_back(act);
+ }
+}
+
+/**
+ * @brief Get the last action performed by a particular Thread
+ * @param tid The thread ID of the Thread in question
+ * @return The last action in the thread
+ */
+ModelAction * ModelChecker::get_last_action(thread_id_t tid) const
+{
+ int threadid = id_to_int(tid);
+ if (threadid < (int)thrd_last_action->size())
+ return (*thrd_last_action)[id_to_int(tid)];
+ else
+ return NULL;
}
-ModelAction * ModelChecker::get_last_action(thread_id_t tid)
+/**
+ * @brief Get the last fence release performed by a particular Thread
+ * @param tid The thread ID of the Thread in question
+ * @return The last fence release in the thread, if one exists; NULL otherwise
+ */
+ModelAction * ModelChecker::get_last_fence_release(thread_id_t tid) const
{
- int nthreads = get_num_threads();
- if ((int)thrd_last_action->size() < nthreads)
- thrd_last_action->resize(nthreads);
- return (*thrd_last_action)[id_to_int(tid)];
+ int threadid = id_to_int(tid);
+ if (threadid < (int)thrd_last_fence_release->size())
+ return (*thrd_last_fence_release)[id_to_int(tid)];
+ else
+ return NULL;
}
/**
- * Gets the last memory_order_seq_cst action (in the total global sequence)
- * performed on a particular object (i.e., memory location).
- * @param location The object location to check
- * @return The last seq_cst action performed
+ * Gets the last memory_order_seq_cst write (in the total global sequence)
+ * performed on a particular object (i.e., memory location), not including the
+ * current action.
+ * @param curr The current ModelAction; also denotes the object location to
+ * check
+ * @return The last seq_cst write
*/
-ModelAction * ModelChecker::get_last_seq_cst(const void *location)
+ModelAction * ModelChecker::get_last_seq_cst_write(ModelAction *curr) const
{
- action_list_t *list = obj_map->get_safe_ptr(location);
+ void *location = curr->get_location();
+ action_list_t *list = get_safe_ptr_action(obj_map, location);
/* Find: max({i in dom(S) | seq_cst(t_i) && isWrite(t_i) && samevar(t_i, t)}) */
action_list_t::reverse_iterator rit;
for (rit = list->rbegin(); rit != list->rend(); rit++)
- if ((*rit)->is_write() && (*rit)->is_seqcst())
+ if ((*rit)->is_write() && (*rit)->is_seqcst() && (*rit) != curr)
+ return *rit;
+ return NULL;
+}
+
+/**
+ * Gets the last memory_order_seq_cst fence (in the total global sequence)
+ * performed in a particular thread, prior to a particular fence.
+ * @param tid The ID of the thread to check
+ * @param before_fence The fence from which to begin the search; if NULL, then
+ * search for the most recent fence in the thread.
+ * @return The last prior seq_cst fence in the thread, if exists; otherwise, NULL
+ */
+ModelAction * ModelChecker::get_last_seq_cst_fence(thread_id_t tid, const ModelAction *before_fence) const
+{
+ /* All fences should have NULL location */
+ action_list_t *list = get_safe_ptr_action(obj_map, NULL);
+ action_list_t::reverse_iterator rit = list->rbegin();
+
+ if (before_fence) {
+ for (; rit != list->rend(); rit++)
+ if (*rit == before_fence)
+ break;
+
+ ASSERT(*rit == before_fence);
+ rit++;
+ }
+
+ for (; rit != list->rend(); rit++)
+ if ((*rit)->is_fence() && (tid == (*rit)->get_tid()) && (*rit)->is_seqcst())
+ return *rit;
+ return NULL;
+}
+
+/**
+ * Gets the last unlock operation performed on a particular mutex (i.e., memory
+ * location). This function identifies the mutex according to the current
+ * action, which is presumed to perform on the same mutex.
+ * @param curr The current ModelAction; also denotes the object location to
+ * check
+ * @return The last unlock operation
+ */
+ModelAction * ModelChecker::get_last_unlock(ModelAction *curr) const
+{
+ void *location = curr->get_location();
+ action_list_t *list = get_safe_ptr_action(obj_map, location);
+ /* Find: max({i in dom(S) | isUnlock(t_i) && samevar(t_i, t)}) */
+ action_list_t::reverse_iterator rit;
+ for (rit = list->rbegin(); rit != list->rend(); rit++)
+ if ((*rit)->is_unlock() || (*rit)->is_wait())
return *rit;
return NULL;
}
-ModelAction * ModelChecker::get_parent_action(thread_id_t tid)
+ModelAction * ModelChecker::get_parent_action(thread_id_t tid) const
{
ModelAction *parent = get_last_action(tid);
if (!parent)
* @param tid The thread whose clock vector we want
* @return Desired clock vector
*/
-ClockVector * ModelChecker::get_cv(thread_id_t tid)
+ClockVector * ModelChecker::get_cv(thread_id_t tid) const
{
return get_parent_action(tid)->get_cv();
}
*/
bool ModelChecker::resolve_promises(ModelAction *write)
{
- bool resolved = false;
+ bool haveResolved = false;
+ std::vector< ModelAction *, ModelAlloc<ModelAction *> > actions_to_check;
+ promise_list_t mustResolve, resolved;
+
for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) {
Promise *promise = (*promises)[promise_index];
if (write->get_node()->get_promise(i)) {
ModelAction *read = promise->get_action();
- read->read_from(write);
- r_modification_order(read, write);
- post_r_modification_order(read, write);
+ read_from(read, write);
+ //Make sure the promise's value matches the write's value
+ ASSERT(promise->is_compatible(write));
+ mo_graph->resolvePromise(read, write, &mustResolve);
+
+ resolved.push_back(promise);
promises->erase(promises->begin() + promise_index);
- resolved = true;
+ actions_to_check.push_back(read);
+
+ haveResolved = true;
} else
promise_index++;
}
- return resolved;
+
+ for (unsigned int i = 0; i < mustResolve.size(); i++) {
+ if (std::find(resolved.begin(), resolved.end(), mustResolve[i])
+ == resolved.end())
+ priv->failed_promise = true;
+ }
+ for (unsigned int i = 0; i < resolved.size(); i++)
+ delete resolved[i];
+ //Check whether reading these writes has made threads unable to
+ //resolve promises
+
+ for (unsigned int i = 0; i < actions_to_check.size(); i++) {
+ ModelAction *read = actions_to_check[i];
+ mo_check_promises(read, true);
+ }
+
+ return haveResolved;
}
/**
const ModelAction *act = promise->get_action();
if (!act->happens_before(curr) &&
act->is_read() &&
- !act->is_synchronizing(curr) &&
+ !act->could_synchronize_with(curr) &&
!act->same_thread(curr) &&
+ act->get_location() == curr->get_location() &&
promise->get_value() == curr->get_value()) {
- curr->get_node()->set_promise(i);
+ curr->get_node()->set_promise(i, act->is_rmw());
}
}
}
/** Checks promises in response to change in ClockVector Threads. */
-void ModelChecker::check_promises(ClockVector *old_cv, ClockVector *merge_cv)
+void ModelChecker::check_promises(thread_id_t tid, ClockVector *old_cv, ClockVector *merge_cv)
{
for (unsigned int i = 0; i < promises->size(); i++) {
Promise *promise = (*promises)[i];
const ModelAction *act = promise->get_action();
if ((old_cv == NULL || !old_cv->synchronized_since(act)) &&
merge_cv->synchronized_since(act)) {
- //This thread is no longer able to send values back to satisfy the promise
- int num_synchronized_threads = promise->increment_threads();
- if (num_synchronized_threads == model->get_num_threads()) {
+ if (promise->eliminate_thread(tid)) {
//Promise has failed
- failed_promise = true;
+ priv->failed_promise = true;
+ return;
+ }
+ }
+ }
+}
+
+void ModelChecker::check_promises_thread_disabled()
+{
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ if (promise->has_failed()) {
+ priv->failed_promise = true;
+ return;
+ }
+ }
+}
+
+/**
+ * @brief Checks promises in response to addition to modification order for
+ * threads.
+ *
+ * We test whether threads are still available for satisfying promises after an
+ * addition to our modification order constraints. Those that are unavailable
+ * are "eliminated". Once all threads are eliminated from satisfying a promise,
+ * that promise has failed.
+ *
+ * @param act The ModelAction which updated the modification order
+ * @param is_read_check Should be true if act is a read and we must check for
+ * updates to the store from which it read (there is a distinction here for
+ * RMW's, which are both a load and a store)
+ */
+void ModelChecker::mo_check_promises(const ModelAction *act, bool is_read_check)
+{
+ const ModelAction *write = is_read_check ? act->get_reads_from() : act;
+
+ for (unsigned int i = 0; i < promises->size(); i++) {
+ Promise *promise = (*promises)[i];
+ const ModelAction *pread = promise->get_action();
+
+ // Is this promise on the same location?
+ if (!pread->same_var(write))
+ continue;
+
+ if (pread->happens_before(act) && mo_graph->checkPromise(write, promise)) {
+ priv->failed_promise = true;
+ return;
+ }
+
+ // Don't do any lookups twice for the same thread
+ if (!promise->thread_is_available(act->get_tid()))
+ continue;
+
+ if (mo_graph->checkReachable(promise, write)) {
+ if (mo_graph->checkPromise(write, promise)) {
+ priv->failed_promise = true;
return;
}
}
}
}
+/**
+ * Compute the set of writes that may break the current pending release
+ * sequence. This information is extracted from previou release sequence
+ * calculations.
+ *
+ * @param curr The current ModelAction. Must be a release sequence fixup
+ * action.
+ */
+void ModelChecker::compute_relseq_breakwrites(ModelAction *curr)
+{
+ if (pending_rel_seqs->empty())
+ return;
+
+ struct release_seq *pending = pending_rel_seqs->back();
+ for (unsigned int i = 0; i < pending->writes.size(); i++) {
+ const ModelAction *write = pending->writes[i];
+ curr->get_node()->add_relseq_break(write);
+ }
+
+ /* NULL means don't break the sequence; just synchronize */
+ curr->get_node()->add_relseq_break(NULL);
+}
+
/**
* Build up an initial set of all past writes that this 'read' action may read
- * from. This set is determined by the clock vector's "happens before"
- * relationship.
+ * from, as well as any previously-observed future values that must still be valid.
+ *
* @param curr is the current ModelAction that we are exploring; it must be a
* 'read' operation.
*/
-void ModelChecker::build_reads_from_past(ModelAction *curr)
+void ModelChecker::build_may_read_from(ModelAction *curr)
{
- std::vector<action_list_t> *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location());
+ std::vector<action_list_t> *thrd_lists = get_safe_ptr_vect_action(obj_thrd_map, curr->get_location());
unsigned int i;
ASSERT(curr->is_read());
- ModelAction *last_seq_cst = NULL;
-
- /* Track whether this object has been initialized */
- bool initialized = false;
+ ModelAction *last_sc_write = NULL;
- if (curr->is_seqcst()) {
- last_seq_cst = get_last_seq_cst(curr->get_location());
- /* We have to at least see the last sequentially consistent write,
- so we are initialized. */
- if (last_seq_cst != NULL)
- initialized = true;
- }
+ if (curr->is_seqcst())
+ last_sc_write = get_last_seq_cst_write(curr);
/* Iterate over all threads */
for (i = 0; i < thrd_lists->size(); i++) {
ModelAction *act = *rit;
/* Only consider 'write' actions */
- if (!act->is_write())
+ if (!act->is_write() || act == curr)
continue;
/* Don't consider more than one seq_cst write if we are a seq_cst read. */
- if (!act->is_seqcst() || !curr->is_seqcst() || act == last_seq_cst) {
- DEBUG("Adding action to may_read_from:\n");
- if (DBG_ENABLED()) {
- act->print();
- curr->print();
- }
- curr->get_node()->add_read_from(act);
+ bool allow_read = true;
+
+ if (curr->is_seqcst() && (act->is_seqcst() || (last_sc_write != NULL && act->happens_before(last_sc_write))) && act != last_sc_write)
+ allow_read = false;
+ else if (curr->get_sleep_flag() && !curr->is_seqcst() && !sleep_can_read_from(curr, act))
+ allow_read = false;
+
+ if (allow_read) {
+ /* Only add feasible reads */
+ mo_graph->startChanges();
+ r_modification_order(curr, act);
+ if (!is_infeasible())
+ curr->get_node()->add_read_from(act);
+ mo_graph->rollbackChanges();
}
/* Include at most one act per-thread that "happens before" curr */
- if (act->happens_before(curr)) {
- initialized = true;
+ if (act->happens_before(curr))
break;
+ }
+ }
+
+ /* Inherit existing, promised future values */
+ for (i = 0; i < promises->size(); i++) {
+ const Promise *promise = (*promises)[i];
+ const ModelAction *promise_read = promise->get_action();
+ if (promise_read->same_var(curr)) {
+ /* Only add feasible future-values */
+ mo_graph->startChanges();
+ r_modification_order(curr, promise);
+ if (!is_infeasible()) {
+ const struct future_value fv = promise->get_fv();
+ curr->get_node()->add_future_value(fv);
}
+ mo_graph->rollbackChanges();
}
}
- if (!initialized) {
- /** @todo Need a more informative way of reporting errors. */
- printf("ERROR: may read from uninitialized atomic\n");
+ /* We may find no valid may-read-from only if the execution is doomed */
+ if (!curr->get_node()->get_read_from_size() && curr->get_node()->future_value_empty()) {
+ priv->no_valid_reads = true;
+ set_assert();
}
- if (DBG_ENABLED() || !initialized) {
- printf("Reached read action:\n");
+ if (DBG_ENABLED()) {
+ model_print("Reached read action:\n");
curr->print();
- printf("Printing may_read_from\n");
+ model_print("Printing may_read_from\n");
curr->get_node()->print_may_read_from();
- printf("End printing may_read_from\n");
+ model_print("End printing may_read_from\n");
+ }
+}
+
+bool ModelChecker::sleep_can_read_from(ModelAction *curr, const ModelAction *write)
+{
+ for ( ; write != NULL; write = write->get_reads_from()) {
+ /* UNINIT actions don't have a Node, and they never sleep */
+ if (write->is_uninitialized())
+ return true;
+ Node *prevnode = write->get_node()->get_parent();
+
+ bool thread_sleep = prevnode->enabled_status(curr->get_tid()) == THREAD_SLEEP_SET;
+ if (write->is_release() && thread_sleep)
+ return true;
+ if (!write->is_rmw())
+ return false;
}
+ return true;
+}
- ASSERT(initialized);
+/**
+ * @brief Create a new action representing an uninitialized atomic
+ * @param location The memory location of the atomic object
+ * @return A pointer to a new ModelAction
+ */
+ModelAction * ModelChecker::new_uninitialized_action(void *location) const
+{
+ ModelAction *act = (ModelAction *)snapshot_malloc(sizeof(class ModelAction));
+ act = new (act) ModelAction(ATOMIC_UNINIT, std::memory_order_relaxed, location, 0, model_thread);
+ act->create_cv(NULL);
+ return act;
}
static void print_list(action_list_t *list)
{
action_list_t::iterator it;
- printf("---------------------------------------------------------------------\n");
- printf("Trace:\n");
+ model_print("---------------------------------------------------------------------\n");
+
+ unsigned int hash = 0;
for (it = list->begin(); it != list->end(); it++) {
(*it)->print();
+ hash = hash^(hash<<3)^((*it)->hash());
}
- printf("---------------------------------------------------------------------\n");
+ model_print("HASH %u\n", hash);
+ model_print("---------------------------------------------------------------------\n");
}
-void ModelChecker::print_summary()
+#if SUPPORT_MOD_ORDER_DUMP
+void ModelChecker::dumpGraph(char *filename) const
{
- printf("\n");
- printf("Number of executions: %d\n", num_executions);
- printf("Total nodes created: %d\n", node_stack->get_total_nodes());
+ char buffer[200];
+ sprintf(buffer, "%s.dot", filename);
+ FILE *file = fopen(buffer, "w");
+ fprintf(file, "digraph %s {\n", filename);
+ mo_graph->dumpNodes(file);
+ ModelAction **thread_array = (ModelAction **)model_calloc(1, sizeof(ModelAction *) * get_num_threads());
+
+ for (action_list_t::iterator it = action_trace->begin(); it != action_trace->end(); it++) {
+ ModelAction *action = *it;
+ if (action->is_read()) {
+ fprintf(file, "N%u [label=\"N%u, T%u\"];\n", action->get_seq_number(), action->get_seq_number(), action->get_tid());
+ if (action->get_reads_from() != NULL)
+ fprintf(file, "N%u -> N%u[label=\"rf\", color=red];\n", action->get_seq_number(), action->get_reads_from()->get_seq_number());
+ }
+ if (thread_array[action->get_tid()] != NULL) {
+ fprintf(file, "N%u -> N%u[label=\"sb\", color=blue];\n", thread_array[action->get_tid()]->get_seq_number(), action->get_seq_number());
+ }
- scheduler->print();
+ thread_array[action->get_tid()] = action;
+ }
+ fprintf(file, "}\n");
+ model_free(thread_array);
+ fclose(file);
+}
+#endif
- if (!isfinalfeasible())
- printf("INFEASIBLE EXECUTION!\n");
+/** @brief Prints an execution trace summary. */
+void ModelChecker::print_summary() const
+{
+#if SUPPORT_MOD_ORDER_DUMP
+ char buffername[100];
+ sprintf(buffername, "exec%04u", stats.num_total);
+ mo_graph->dumpGraphToFile(buffername);
+ sprintf(buffername, "graph%04u", stats.num_total);
+ dumpGraph(buffername);
+#endif
+
+ model_print("Execution %d:", stats.num_total);
+ if (isfeasibleprefix())
+ model_print("\n");
+ else
+ print_infeasibility(" INFEASIBLE");
print_list(action_trace);
- printf("\n");
+ model_print("\n");
}
/**
scheduler->add_thread(t);
}
+/**
+ * Removes a thread from the scheduler.
+ * @param the thread to remove.
+ */
void ModelChecker::remove_thread(Thread *t)
{
scheduler->remove_thread(t);
}
+/**
+ * @brief Get a Thread reference by its ID
+ * @param tid The Thread's ID
+ * @return A Thread reference
+ */
+Thread * ModelChecker::get_thread(thread_id_t tid) const
+{
+ return thread_map->get(id_to_int(tid));
+}
+
+/**
+ * @brief Get a reference to the Thread in which a ModelAction was executed
+ * @param act The ModelAction
+ * @return A Thread reference
+ */
+Thread * ModelChecker::get_thread(const ModelAction *act) const
+{
+ return get_thread(act->get_tid());
+}
+
+/**
+ * @brief Check if a Thread is currently enabled
+ * @param t The Thread to check
+ * @return True if the Thread is currently enabled
+ */
+bool ModelChecker::is_enabled(Thread *t) const
+{
+ return scheduler->is_enabled(t);
+}
+
+/**
+ * @brief Check if a Thread is currently enabled
+ * @param tid The ID of the Thread to check
+ * @return True if the Thread is currently enabled
+ */
+bool ModelChecker::is_enabled(thread_id_t tid) const
+{
+ return scheduler->is_enabled(tid);
+}
+
+/**
+ * Switch from a model-checker context to a user-thread context. This is the
+ * complement of ModelChecker::switch_to_master and must be called from the
+ * model-checker context
+ *
+ * @param thread The user-thread to switch to
+ */
+void ModelChecker::switch_from_master(Thread *thread)
+{
+ scheduler->set_current_thread(thread);
+ Thread::swap(&system_context, thread);
+}
+
/**
* Switch from a user-context to the "master thread" context (a.k.a. system
* context). This switch is made with the intention of exploring a particular
* model-checking action (described by a ModelAction object). Must be called
* from a user-thread context.
- * @param act The current action that will be explored. May be NULL, although
- * there is little reason to switch to the model-checker without an action to
- * explore (note: act == NULL is sometimes used as a hack to allow a thread to
- * yield control without performing any progress; see thrd_join()).
- * @return Return status from the 'swap' call (i.e., success/fail, 0/-1)
+ *
+ * @param act The current action that will be explored. May be NULL only if
+ * trace is exiting via an assertion (see ModelChecker::set_assert and
+ * ModelChecker::has_asserted).
+ * @return Return the value returned by the current action
*/
-int ModelChecker::switch_to_master(ModelAction *act)
+uint64_t ModelChecker::switch_to_master(ModelAction *act)
{
DBG();
Thread *old = thread_current();
- set_current_action(act);
- old->set_state(THREAD_READY);
- return Thread::swap(old, &system_context);
+ ASSERT(!old->get_pending());
+ old->set_pending(act);
+ if (Thread::swap(old, &system_context) < 0) {
+ perror("swap threads");
+ exit(EXIT_FAILURE);
+ }
+ return old->get_return_value();
}
/**
* Takes the next step in the execution, if possible.
- * @return Returns true (success) if a step was taken and false otherwise.
- */
-bool ModelChecker::take_step() {
- Thread *curr, *next;
-
- curr = thread_current();
- if (curr) {
- if (curr->get_state() == THREAD_READY) {
- check_current_action();
- scheduler->add_thread(curr);
- } else if (curr->get_state() == THREAD_RUNNING) {
- /* Stopped while running; i.e., completed */
- curr->complete();
- } else {
- ASSERT(false);
- }
- }
- next = scheduler->next_thread();
+ * @param curr The current step to take
+ * @return Returns the next Thread to run, if any; NULL if this execution
+ * should terminate
+ */
+Thread * ModelChecker::take_step(ModelAction *curr)
+{
+ Thread *curr_thrd = get_thread(curr);
+ ASSERT(curr_thrd->get_state() == THREAD_READY);
+
+ curr = check_current_action(curr);
/* Infeasible -> don't take any more steps */
- if (!isfeasible())
- return false;
+ if (is_infeasible())
+ return NULL;
+ else if (isfeasibleprefix() && have_bug_reports()) {
+ set_assert();
+ return NULL;
+ }
+
+ if (params.bound != 0 && priv->used_sequence_numbers > params.bound)
+ return NULL;
- if (next)
- next->set_state(THREAD_RUNNING);
- DEBUG("(%d, %d)\n", curr ? curr->get_id() : -1, next ? next->get_id() : -1);
+ if (curr_thrd->is_blocked() || curr_thrd->is_complete())
+ scheduler->remove_thread(curr_thrd);
- /* next == NULL -> don't take any more steps */
- if (!next)
- return false;
- /* Return false only if swap fails with an error */
- return (Thread::swap(&system_context, next) == 0);
+ Thread *next_thrd = get_next_thread(curr);
+
+ DEBUG("(%d, %d)\n", curr_thrd ? id_to_int(curr_thrd->get_id()) : -1,
+ next_thrd ? id_to_int(next_thrd->get_id()) : -1);
+
+ return next_thrd;
}
-/** Runs the current execution until threre are no more steps to take. */
-void ModelChecker::finish_execution() {
- DBG();
+/** Wrapper to run the user's main function, with appropriate arguments */
+void user_main_wrapper(void *)
+{
+ user_main(model->params.argc, model->params.argv);
+}
+
+/** @brief Run ModelChecker for the user program */
+void ModelChecker::run()
+{
+ do {
+ thrd_t user_thread;
+ Thread *t = new Thread(&user_thread, &user_main_wrapper, NULL);
+ add_thread(t);
+
+ do {
+ /*
+ * Stash next pending action(s) for thread(s). There
+ * should only need to stash one thread's action--the
+ * thread which just took a step--plus the first step
+ * for any newly-created thread
+ */
+ for (unsigned int i = 0; i < get_num_threads(); i++) {
+ thread_id_t tid = int_to_id(i);
+ Thread *thr = get_thread(tid);
+ if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
+ switch_from_master(thr);
+ }
+ }
+
+ /* Catch assertions from prior take_step or from
+ * between-ModelAction bugs (e.g., data races) */
+ if (has_asserted())
+ break;
- while (take_step());
+ /* Consume the next action for a Thread */
+ ModelAction *curr = t->get_pending();
+ t->set_pending(NULL);
+ t = take_step(curr);
+ } while (t && !t->is_model_thread());
+
+ /*
+ * Launch end-of-execution release sequence fixups only when
+ * the execution is otherwise feasible AND there are:
+ *
+ * (1) pending release sequences
+ * (2) pending assertions that could be invalidated by a change
+ * in clock vectors (i.e., data races)
+ * (3) no pending promises
+ */
+ while (!pending_rel_seqs->empty() &&
+ is_feasible_prefix_ignore_relseq() &&
+ !unrealizedraces.empty()) {
+ model_print("*** WARNING: release sequence fixup action "
+ "(%zu pending release seuqence(s)) ***\n",
+ pending_rel_seqs->size());
+ ModelAction *fixup = new ModelAction(MODEL_FIXUP_RELSEQ,
+ std::memory_order_seq_cst, NULL, VALUE_NONE,
+ model_thread);
+ take_step(fixup);
+ };
+ } while (next_execution());
+
+ model_print("******* Model-checking complete: *******\n");
+ print_stats();
}
projects / model-checker.git / blobdiff