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another try to avoid the race with atomic swap

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Signed-off-by: Lev Nachmanson <levnach@hotmail.com>
This commit is contained in:
Lev Nachmanson 2025-07-02 18:14:29 -07:00
parent 5b2226127e
commit 2b3d2ea055
1 changed files with 67 additions and 56 deletions
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123
src/smt/tactic/smt_tactic_core.cpp
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@ -44,8 +44,7 @@ class smt_tactic : public tactic {
expr_ref_vector m_vars;
vector<std::pair<expr_ref, expr_ref>> m_values;
statistics m_stats;
smt::kernel* m_ctx = nullptr;
mutable std::atomic<bool> m_ctx_destroying;
mutable std::atomic<smt::kernel*> m_ctx;
symbol m_logic;
progress_callback* m_callback = nullptr;
bool m_candidate_models = false;
@ -56,7 +55,7 @@ public:
m(m),
m_params_ref(p),
m_vars(m),
m_ctx_destroying(false) {
m_ctx(nullptr) {
updt_params_core(p);
TRACE(smt_tactic, tout << "p: " << p << "\n";);
}
@ -66,7 +65,7 @@ public:
}
~smt_tactic() override {
SASSERT(m_ctx == nullptr);
SASSERT(m_ctx.load() == nullptr);
}
char const* name() const override { return "smt"; }
@ -91,8 +90,8 @@ public:
fparams().updt_params(p);
m_params_ref.copy(p);
m_logic = p.get_sym(symbol("logic"), m_logic);
if (m_logic != symbol::null && m_ctx) {
m_ctx->set_logic(m_logic);
if (m_logic != symbol::null && m_ctx.load()) {
m_ctx.load()->set_logic(m_logic);
}
SASSERT(p.get_bool("auto_config", fparams().m_auto_config) == fparams().m_auto_config);
}
@ -104,15 +103,25 @@ public:
void collect_statistics(statistics & st) const override {
// Check if context is being destroyed to avoid race condition
if (!m_ctx_destroying.load() && m_ctx) {
try {
m_ctx->collect_statistics(st);
// Use compare_exchange to safely extract the context pointer
// If we win the race, we're responsible for deallocation
smt::kernel* ctx = m_ctx.load();
if (ctx) {
// Try to atomically swap the context with nullptr
// If successful, we own the context and must deallocate it
if (m_ctx.compare_exchange_strong(ctx, nullptr)) {
try {
ctx->collect_statistics(st);
} catch (...) {
// If exception occurs, fall back to cached stats
st.copy(m_stats);
}
// We won the race, so we're responsible for cleanup
dealloc(ctx);
return;
} catch (...) {
// If exception occurs, fall back to cached stats
}
}
// Either no context or lost the race - use cached stats
st.copy(m_stats);
}
@ -131,6 +140,12 @@ public:
m_callback = callback;
}
private:
// Helper to safely get context pointer (only use within scoped_init_ctx lifetime)
smt::kernel* get_ctx() const { return m_ctx.load(); }
public:
struct scoped_init_ctx {
smt_tactic & m_owner;
smt_params m_params; // smt-setup overwrites parameters depending on the current assertions.
@ -146,22 +161,18 @@ public:
if (o.m_callback) {
new_ctx->set_progress_callback(o.m_callback);
}
o.m_ctx = new_ctx;
o.m_ctx.store(new_ctx);
}
~scoped_init_ctx() {
// Signal that we're destroying the context
m_owner.m_ctx_destroying.store(true);
smt::kernel * d = m_owner.m_ctx;
m_owner.m_ctx = nullptr;
m_owner.m_user_ctx = nullptr;
if (d)
dealloc(d);
// Reset the flag after cleanup
m_owner.m_ctx_destroying.store(false);
// Try to atomically swap the context with nullptr
smt::kernel* ctx = m_owner.m_ctx.load();
if (ctx && m_owner.m_ctx.compare_exchange_strong(ctx, nullptr)) {
// We won the race, so we're responsible for cleanup
m_owner.m_user_ctx = nullptr;
dealloc(ctx);
}
// If we lost the race, collect_statistics() is handling the cleanup
}
};
@ -184,7 +195,7 @@ public:
TRACE(smt_tactic_detail, in->display(tout););
TRACE(smt_tactic_memory, tout << "wasted_size: " << m.get_allocator().get_wasted_size() << "\n";);
scoped_init_ctx init(*this, m);
SASSERT(m_ctx);
SASSERT(m_ctx.load());
expr_ref_vector clauses(m);
expr2expr_map bool2dep;
@ -197,22 +208,22 @@ public:
if (in->proofs_enabled() && !assumptions.empty())
throw tactic_exception("smt tactic does not support simultaneous generation of proofs and unsat cores");
for (unsigned i = 0; i < clauses.size(); ++i) {
m_ctx->assert_expr(clauses[i].get());
get_ctx()->assert_expr(clauses[i].get());
}
}
else if (in->proofs_enabled()) {
unsigned sz = in->size();
for (unsigned i = 0; i < sz; i++) {
m_ctx->assert_expr(in->form(i), in->pr(i));
get_ctx()->assert_expr(in->form(i), in->pr(i));
}
}
else {
unsigned sz = in->size();
for (unsigned i = 0; i < sz; i++) {
m_ctx->assert_expr(in->form(i));
get_ctx()->assert_expr(in->form(i));
}
}
if (m_ctx->canceled()) {
if (get_ctx()->canceled()) {
throw tactic_exception(Z3_CANCELED_MSG);
}
user_propagate_delay_init();
@ -220,18 +231,18 @@ public:
lbool r;
try {
if (assumptions.empty() && !m_user_ctx)
r = m_ctx->setup_and_check();
r = get_ctx()->setup_and_check();
else
r = m_ctx->check(assumptions.size(), assumptions.data());
r = get_ctx()->check(assumptions.size(), assumptions.data());
}
catch(...) {
TRACE(smt_tactic, tout << "exception\n";);
m_ctx->collect_statistics(m_stats);
get_ctx()->collect_statistics(m_stats);
throw;
}
SASSERT(m_ctx);
m_ctx->collect_statistics(m_stats);
proof_ref pr(m_ctx->get_proof(), m);
get_ctx()->collect_statistics(m_stats);
proof_ref pr(get_ctx()->get_proof(), m);
TRACE(smt_tactic, tout << r << " " << pr << "\n";);
switch (r) {
case l_true: {
@ -243,9 +254,9 @@ public:
// store the model in a no-op model converter, and filter fresh Booleans
if (in->models_enabled()) {
model_ref md;
m_ctx->get_model(md);
get_ctx()->get_model(md);
buffer<symbol> r;
m_ctx->get_relevant_labels(nullptr, r);
get_ctx()->get_relevant_labels(nullptr, r);
labels_vec rv;
rv.append(r.size(), r.data());
model_converter_ref mc;
@ -253,7 +264,7 @@ public:
mc = concat(fmc.get(), mc.get());
in->add(mc.get());
}
if (m_ctx->canceled())
if (get_ctx()->canceled())
throw tactic_exception(Z3_CANCELED_MSG);
return;
}
@ -266,9 +277,9 @@ public:
in->reset();
expr_dependency * lcore = nullptr;
if (in->unsat_core_enabled()) {
unsigned sz = m_ctx->get_unsat_core_size();
unsigned sz = get_ctx()->get_unsat_core_size();
for (unsigned i = 0; i < sz; i++) {
expr * b = m_ctx->get_unsat_core_expr(i);
expr * b = get_ctx()->get_unsat_core_expr(i);
SASSERT(is_uninterp_const(b) && m.is_bool(b));
expr * d = bool2dep.find(b);
lcore = m.mk_join(lcore, m.mk_leaf(d));
@ -284,13 +295,13 @@ public:
}
case l_undef:
if (m_ctx->canceled() && !pr) {
if (get_ctx()->canceled() && !pr) {
throw tactic_exception(Z3_CANCELED_MSG);
}
if (m_fail_if_inconclusive && !m_candidate_models && !pr) {
std::stringstream strm;
strm << "smt tactic failed to show goal to be sat/unsat " << m_ctx->last_failure_as_string();
strm << "smt tactic failed to show goal to be sat/unsat " << get_ctx()->last_failure_as_string();
throw tactic_exception(strm.str());
}
result.push_back(in.get());
@ -300,15 +311,15 @@ public:
in->updt_prec(goal::UNDER_OVER);
}
if (m_candidate_models) {
switch (m_ctx->last_failure()) {
switch (get_ctx()->last_failure()) {
case smt::NUM_CONFLICTS:
case smt::THEORY:
case smt::QUANTIFIERS:
if (in->models_enabled()) {
model_ref md;
m_ctx->get_model(md);
get_ctx()->get_model(md);
buffer<symbol> r;
m_ctx->get_relevant_labels(nullptr, r);
get_ctx()->get_relevant_labels(nullptr, r);
labels_vec rv;
rv.append(r.size(), r.data());
in->add(model_and_labels2model_converter(md.get(), rv));
@ -321,7 +332,7 @@ public:
if (pr) {
return;
}
throw tactic_exception(m_ctx->last_failure_as_string());
throw tactic_exception(get_ctx()->last_failure_as_string());
}
}
catch (rewriter_exception & ex) {
@ -344,24 +355,24 @@ public:
void on_clause_delay_init() {
if (m_on_clause_eh)
m_ctx->register_on_clause(m_on_clause_ctx, m_on_clause_eh);
get_ctx()->register_on_clause(m_on_clause_ctx, m_on_clause_eh);
}
void user_propagate_delay_init() {
if (!m_user_ctx)
return;
m_ctx->user_propagate_init(m_user_ctx, m_push_eh, m_pop_eh, m_fresh_eh);
if (m_fixed_eh) m_ctx->user_propagate_register_fixed(m_fixed_eh);
if (m_final_eh) m_ctx->user_propagate_register_final(m_final_eh);
if (m_eq_eh) m_ctx->user_propagate_register_eq(m_eq_eh);
if (m_diseq_eh) m_ctx->user_propagate_register_diseq(m_diseq_eh);
if (m_created_eh) m_ctx->user_propagate_register_created(m_created_eh);
if (m_decide_eh) m_ctx->user_propagate_register_decide(m_decide_eh);
get_ctx()->user_propagate_init(m_user_ctx, m_push_eh, m_pop_eh, m_fresh_eh);
if (m_fixed_eh) get_ctx()->user_propagate_register_fixed(m_fixed_eh);
if (m_final_eh) get_ctx()->user_propagate_register_final(m_final_eh);
if (m_eq_eh) get_ctx()->user_propagate_register_eq(m_eq_eh);
if (m_diseq_eh) get_ctx()->user_propagate_register_diseq(m_diseq_eh);
if (m_created_eh) get_ctx()->user_propagate_register_created(m_created_eh);
if (m_decide_eh) get_ctx()->user_propagate_register_decide(m_decide_eh);
for (expr* v : m_vars)
m_ctx->user_propagate_register_expr(v);
get_ctx()->user_propagate_register_expr(v);
for (auto& [var, value] : m_values)
m_ctx->user_propagate_initialize_value(var, value);
get_ctx()->user_propagate_initialize_value(var, value);
}
void user_propagate_clear() override {