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#include <pybind11/critical_section.h>
#include "pybind11_tests.h"
#include <atomic>
#include <chrono>
#include <thread>
#include <utility>
#if defined(PYBIND11_CPP20) && defined(__has_include) && __has_include(<barrier>)
# define PYBIND11_HAS_BARRIER 1
# include <barrier>
#endif
namespace test_scoped_critical_section_ns {
void test_one_nullptr() { py::scoped_critical_section lock{py::handle{}}; }
void test_two_nullptrs() { py::scoped_critical_section lock{py::handle{}, py::handle{}}; }
void test_first_nullptr() {
py::dict d;
py::scoped_critical_section lock{py::handle{}, d};
}
void test_second_nullptr() {
py::dict d;
py::scoped_critical_section lock{d, py::handle{}};
}
// Referenced test implementation: https://github.com/PyO3/pyo3/blob/v0.25.0/src/sync.rs#L874
class BoolWrapper {
public:
explicit BoolWrapper(bool value) : value_{value} {}
bool get() const { return value_.load(std::memory_order_acquire); }
void set(bool value) { value_.store(value, std::memory_order_release); }
private:
std::atomic_bool value_{false};
};
#if defined(PYBIND11_HAS_BARRIER)
// Modifying the C/C++ members of a Python object from multiple threads requires a critical section
// to ensure thread safety and data integrity.
// These tests use a scoped critical section to ensure that the Python object is accessed in a
// thread-safe manner.
void test_scoped_critical_section(const py::handle &cls) {
auto barrier = std::barrier(2);
auto bool_wrapper = cls(false);
bool output = false;
{
// Release the GIL to allow run threads in parallel.
py::gil_scoped_release gil_release{};
std::thread t1([&]() {
// Use gil_scoped_acquire to ensure we have a valid Python thread state
// before entering the critical section. Otherwise, the critical section
// will cause a segmentation fault.
py::gil_scoped_acquire ensure_tstate{};
// Enter the critical section with the same object as the second thread.
py::scoped_critical_section lock{bool_wrapper};
// At this point, the object is locked by this thread via the scoped_critical_section.
// This barrier will ensure that the second thread waits until this thread has released
// the critical section before proceeding.
barrier.arrive_and_wait();
// Sleep for a short time to simulate some work in the critical section.
// This sleep is necessary to test the locking mechanism properly.
std::this_thread::sleep_for(std::chrono::milliseconds(10));
auto *bw = bool_wrapper.cast<BoolWrapper *>();
bw->set(true);
});
std::thread t2([&]() {
// This thread will wait until the first thread has entered the critical section due to
// the barrier.
barrier.arrive_and_wait();
{
// Use gil_scoped_acquire to ensure we have a valid Python thread state
// before entering the critical section. Otherwise, the critical section
// will cause a segmentation fault.
py::gil_scoped_acquire ensure_tstate{};
// Enter the critical section with the same object as the first thread.
py::scoped_critical_section lock{bool_wrapper};
// At this point, the critical section is released by the first thread, the value
// is set to true.
auto *bw = bool_wrapper.cast<BoolWrapper *>();
output = bw->get();
}
});
t1.join();
t2.join();
}
if (!output) {
throw std::runtime_error("Scoped critical section test failed: output is false");
}
}
void test_scoped_critical_section2(const py::handle &cls) {
auto barrier = std::barrier(3);
auto bool_wrapper1 = cls(false);
auto bool_wrapper2 = cls(false);
std::pair<bool, bool> output{false, false};
{
// Release the GIL to allow run threads in parallel.
py::gil_scoped_release gil_release{};
std::thread t1([&]() {
// Use gil_scoped_acquire to ensure we have a valid Python thread state
// before entering the critical section. Otherwise, the critical section
// will cause a segmentation fault.
py::gil_scoped_acquire ensure_tstate{};
// Enter the critical section with two different objects.
// This will ensure that the critical section is locked for both objects.
py::scoped_critical_section lock{bool_wrapper1, bool_wrapper2};
// At this point, objects are locked by this thread via the scoped_critical_section.
// This barrier will ensure that other threads wait until this thread has released
// the critical section before proceeding.
barrier.arrive_and_wait();
// Sleep for a short time to simulate some work in the critical section.
// This sleep is necessary to test the locking mechanism properly.
std::this_thread::sleep_for(std::chrono::milliseconds(10));
auto *bw1 = bool_wrapper1.cast<BoolWrapper *>();
auto *bw2 = bool_wrapper2.cast<BoolWrapper *>();
bw1->set(true);
bw2->set(true);
});
std::thread t2([&]() {
// This thread will wait until the first thread has entered the critical section due to
// the barrier.
barrier.arrive_and_wait();
{
// Use gil_scoped_acquire to ensure we have a valid Python thread state
// before entering the critical section. Otherwise, the critical section
// will cause a segmentation fault.
py::gil_scoped_acquire ensure_tstate{};
// Enter the critical section with the same object as the first thread.
py::scoped_critical_section lock{bool_wrapper1};
// At this point, the critical section is released by the first thread, the value
// is set to true.
auto *bw1 = bool_wrapper1.cast<BoolWrapper *>();
output.first = bw1->get();
}
});
std::thread t3([&]() {
// This thread will wait until the first thread has entered the critical section due to
// the barrier.
barrier.arrive_and_wait();
{
// Use gil_scoped_acquire to ensure we have a valid Python thread state
// before entering the critical section. Otherwise, the critical section
// will cause a segmentation fault.
py::gil_scoped_acquire ensure_tstate{};
// Enter the critical section with the same object as the first thread.
py::scoped_critical_section lock{bool_wrapper2};
// At this point, the critical section is released by the first thread, the value
// is set to true.
auto *bw2 = bool_wrapper2.cast<BoolWrapper *>();
output.second = bw2->get();
}
});
t1.join();
t2.join();
t3.join();
}
if (!output.first || !output.second) {
throw std::runtime_error(
"Scoped critical section test with two objects failed: output is false");
}
}
void test_scoped_critical_section2_same_object_no_deadlock(const py::handle &cls) {
auto barrier = std::barrier(2);
auto bool_wrapper = cls(false);
bool output = false;
{
// Release the GIL to allow run threads in parallel.
py::gil_scoped_release gil_release{};
std::thread t1([&]() {
// Use gil_scoped_acquire to ensure we have a valid Python thread state
// before entering the critical section. Otherwise, the critical section
// will cause a segmentation fault.
py::gil_scoped_acquire ensure_tstate{};
// Enter the critical section with the same object as the second thread.
py::scoped_critical_section lock{bool_wrapper, bool_wrapper}; // same object used here
// At this point, the object is locked by this thread via the scoped_critical_section.
// This barrier will ensure that the second thread waits until this thread has released
// the critical section before proceeding.
barrier.arrive_and_wait();
// Sleep for a short time to simulate some work in the critical section.
// This sleep is necessary to test the locking mechanism properly.
std::this_thread::sleep_for(std::chrono::milliseconds(10));
auto *bw = bool_wrapper.cast<BoolWrapper *>();
bw->set(true);
});
std::thread t2([&]() {
// This thread will wait until the first thread has entered the critical section due to
// the barrier.
barrier.arrive_and_wait();
{
// Use gil_scoped_acquire to ensure we have a valid Python thread state
// before entering the critical section. Otherwise, the critical section
// will cause a segmentation fault.
py::gil_scoped_acquire ensure_tstate{};
// Enter the critical section with the same object as the first thread.
py::scoped_critical_section lock{bool_wrapper};
// At this point, the critical section is released by the first thread, the value
// is set to true.
auto *bw = bool_wrapper.cast<BoolWrapper *>();
output = bw->get();
}
});
t1.join();
t2.join();
}
if (!output) {
throw std::runtime_error(
"Scoped critical section test with same object failed: output is false");
}
}
#else
void test_scoped_critical_section(const py::handle &) {}
void test_scoped_critical_section2(const py::handle &) {}
void test_scoped_critical_section2_same_object_no_deadlock(const py::handle &) {}
#endif
} // namespace test_scoped_critical_section_ns
TEST_SUBMODULE(scoped_critical_section, m) {
using namespace test_scoped_critical_section_ns;
m.def("test_one_nullptr", test_one_nullptr);
m.def("test_two_nullptrs", test_two_nullptrs);
m.def("test_first_nullptr", test_first_nullptr);
m.def("test_second_nullptr", test_second_nullptr);
auto BoolWrapperClass = py::class_<BoolWrapper>(m, "BoolWrapper")
.def(py::init<bool>())
.def("get", &BoolWrapper::get)
.def("set", &BoolWrapper::set);
auto BoolWrapperHandle = py::handle(BoolWrapperClass);
(void) BoolWrapperHandle.ptr(); // suppress unused variable warning
m.attr("has_barrier") =
#ifdef PYBIND11_HAS_BARRIER
true;
#else
false;
#endif
m.def("test_scoped_critical_section",
[BoolWrapperHandle]() -> void { test_scoped_critical_section(BoolWrapperHandle); });
m.def("test_scoped_critical_section2",
[BoolWrapperHandle]() -> void { test_scoped_critical_section2(BoolWrapperHandle); });
m.def("test_scoped_critical_section2_same_object_no_deadlock", [BoolWrapperHandle]() -> void {
test_scoped_critical_section2_same_object_no_deadlock(BoolWrapperHandle);
});
}
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