cpython/Modules/_testinternalcapi/test_lock.c at main · python/cpython · GitHub

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// C Extension module to test pycore_lock.h API

#include "parts.h"

#include "pycore_lock.h"

#include "pycore_pythread.h" // PyThread_get_thread_ident_ex()

#include "clinic/test_lock.c.h"

#ifdef MS_WINDOWS

#define WIN32_LEAN_AND_MEAN

#include <windows.h>

#else

#include <unistd.h> // usleep()

#endif

/*[clinic input]

module _testinternalcapi

[clinic start generated code]*/

/*[clinic end generated code: output=da39a3ee5e6b4b0d input=7bb583d8c9eb9a78]*/

static void

pysleep(int ms)

{

#ifdef MS_WINDOWS

Sleep(ms);

#else

usleep(ms * 1000);

#endif

}

static PyObject *

test_lock_basic(PyObject *self, PyObject *obj)

{

PyMutex m = (PyMutex){0};

// uncontended lock and unlock

PyMutex_Lock(&m);

assert(m._bits == 1);

PyMutex_Unlock(&m);

assert(m._bits == 0);

Py_RETURN_NONE;

}

struct test_lock2_data {

PyMutex m;

PyEvent done;

int started;

};

static void

lock_thread(void *arg)

{

struct test_lock2_data *test_data = arg;

PyMutex *m = &test_data->m;

_Py_atomic_store_int(&test_data->started, 1);

PyMutex_Lock(m);

// gh-135641: in rare cases the lock may still have `_Py_HAS_PARKED` set

// (m->_bits == 3) due to bucket collisions in the parking lot hash table

// between this mutex and the `test_data.done` event.

assert(m->_bits == 1 || m->_bits == 3);

PyMutex_Unlock(m);

assert(m->_bits == 0);

_PyEvent_Notify(&test_data->done);

}

static PyObject *

test_lock_two_threads(PyObject *self, PyObject *obj)

{

// lock attempt by two threads

struct test_lock2_data test_data;

memset(&test_data, 0, sizeof(test_data));

PyMutex_Lock(&test_data.m);

assert(test_data.m._bits == 1);

PyThread_start_new_thread(lock_thread, &test_data);

// wait up to two seconds for the lock_thread to attempt to lock "m"

int iters = 0;

uint8_t v;

do {

pysleep(10); // allow some time for the other thread to try to lock

v = _Py_atomic_load_uint8_relaxed(&test_data.m._bits);

assert(v == 1 || v == 3);

iters++;

} while (v != 3 && iters < 200);

// both the "locked" and the "has parked" bits should be set

v = _Py_atomic_load_uint8_relaxed(&test_data.m._bits);

assert(v == 3);

PyMutex_Unlock(&test_data.m);

PyEvent_Wait(&test_data.done);

assert(test_data.m._bits == 0);

Py_RETURN_NONE;

}

#define COUNTER_THREADS 5

#define COUNTER_ITERS 10000

struct test_data_counter {

PyMutex m;

Py_ssize_t counter;

};

struct thread_data_counter {

struct test_data_counter *test_data;

PyEvent done_event;

};

static void

counter_thread(void *arg)

{

struct thread_data_counter *thread_data = arg;

struct test_data_counter *test_data = thread_data->test_data;

for (Py_ssize_t i = 0; i < COUNTER_ITERS; i++) {

PyMutex_Lock(&test_data->m);

test_data->counter++;

PyMutex_Unlock(&test_data->m);

}

_PyEvent_Notify(&thread_data->done_event);

}

static PyObject *

test_lock_counter(PyObject *self, PyObject *obj)

{

// Test with rapidly locking and unlocking mutex

struct test_data_counter test_data;

memset(&test_data, 0, sizeof(test_data));

struct thread_data_counter thread_data[COUNTER_THREADS];

memset(&thread_data, 0, sizeof(thread_data));

for (Py_ssize_t i = 0; i < COUNTER_THREADS; i++) {

thread_data[i].test_data = &test_data;

PyThread_start_new_thread(counter_thread, &thread_data[i]);

}

for (Py_ssize_t i = 0; i < COUNTER_THREADS; i++) {

PyEvent_Wait(&thread_data[i].done_event);

}

assert(test_data.counter == COUNTER_THREADS * COUNTER_ITERS);

Py_RETURN_NONE;

}

#define SLOW_COUNTER_ITERS 100

static void

slow_counter_thread(void *arg)

{

struct thread_data_counter *thread_data = arg;

struct test_data_counter *test_data = thread_data->test_data;

for (Py_ssize_t i = 0; i < SLOW_COUNTER_ITERS; i++) {

PyMutex_Lock(&test_data->m);

if (i % 7 == 0) {

pysleep(2);

}

test_data->counter++;

PyMutex_Unlock(&test_data->m);

}

_PyEvent_Notify(&thread_data->done_event);

}

static PyObject *

test_lock_counter_slow(PyObject *self, PyObject *obj)

{

// Test lock/unlock with occasional "long" critical section, which will

// trigger handoff of the lock.

struct test_data_counter test_data;

memset(&test_data, 0, sizeof(test_data));

struct thread_data_counter thread_data[COUNTER_THREADS];

memset(&thread_data, 0, sizeof(thread_data));

for (Py_ssize_t i = 0; i < COUNTER_THREADS; i++) {

thread_data[i].test_data = &test_data;

PyThread_start_new_thread(slow_counter_thread, &thread_data[i]);

}

for (Py_ssize_t i = 0; i < COUNTER_THREADS; i++) {

PyEvent_Wait(&thread_data[i].done_event);

}

assert(test_data.counter == COUNTER_THREADS * SLOW_COUNTER_ITERS);

Py_RETURN_NONE;

}

struct bench_lock {

char padding[200];

PyMutex m;

double value;

};

struct bench_config {

int stop;

int work_inside;

int work_outside;

int num_acquisitions;

int random_locks;

Py_ssize_t target_iters;

Py_ssize_t num_locks;

struct bench_lock *locks;

};

struct bench_thread_data {

struct bench_config *config;

struct bench_lock *lock;

uint64_t rng_state;

Py_ssize_t iters;

PyEvent done;

};

static uint64_t

splitmix64(uint64_t *state)

{

uint64_t z = (*state += 0x9e3779b97f4a7c15);

z = (z ^ (z >> 30)) * 0xbf58476d1ce4e5b9;

z = (z ^ (z >> 27)) * 0x94d049bb133111eb;

return z ^ (z >> 31);

}

static void

thread_benchmark_locks(void *arg)

{

struct bench_thread_data *td = arg;

struct bench_config *config = td->config;

int work_inside = config->work_inside;

int work_outside = config->work_outside;

int num_acquisitions = config->num_acquisitions;

Py_ssize_t target_iters = config->target_iters;

uint64_t rng_state = td->rng_state;

double local_value = 0.0;

double my_value = 1.0;

Py_ssize_t iters = 0;

for (;;) {

if (target_iters > 0) {

if (iters >= target_iters) {

break;

}

else if (_Py_atomic_load_int_relaxed(&config->stop)) {

break;

}

struct bench_lock *lock = td->lock;

if (config->random_locks) {

uint32_t r = (uint32_t)splitmix64(&rng_state);

// Fast modulo reduction to pick a random lock, adapted from:

// https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/

Py_ssize_t idx = ((uint64_t)r * (uint32_t)config->num_locks) >> 32;

lock = &config->locks[idx];

}

for (int acq = 0; acq < num_acquisitions; acq++) {

PyMutex_Lock(&lock->m);

for (int i = 0; i < work_inside; i++) {

lock->value += my_value;

my_value = lock->value;

}

PyMutex_Unlock(&lock->m);

}

for (int i = 0; i < work_outside; i++) {

local_value += my_value;

my_value = local_value;

}

iters += num_acquisitions;

}

td->iters = iters;

_PyEvent_Notify(&td->done);

}

/*[clinic input]

_testinternalcapi.benchmark_locks

num_threads: Py_ssize_t

work_inside: int = 1

work_outside: int = 0

time_ms: int = 1000

num_acquisitions: int = 1

total_iters: Py_ssize_t = 0

num_locks: Py_ssize_t = 1

random_locks: bool = False

[clinic start generated code]*/

static PyObject *

_testinternalcapi_benchmark_locks_impl(PyObject *module,

Py_ssize_t num_threads,

int work_inside, int work_outside,

int time_ms, int num_acquisitions,

Py_ssize_t total_iters,

Py_ssize_t num_locks,

int random_locks)

/*[clinic end generated code: output=6258dc9de8cb9af1 input=d622cf4e1c4d008b]*/

{

// Run from Tools/lockbench/lockbench.py

// Based on the WebKit lock benchmarks:

// https://github.com/WebKit/WebKit/blob/main/Source/WTF/benchmarks/LockSpeedTest.cpp

// See also https://webkit.org/blog/6161/locking-in-webkit/

PyObject *thread_iters = NULL;

PyObject *res = NULL;

struct bench_thread_data *thread_data = NULL;

struct bench_config config = {

.work_inside = work_inside,

.work_outside = work_outside,

.num_acquisitions = num_acquisitions,

.target_iters = total_iters,

.num_locks = num_locks,

.random_locks = random_locks,

};

config.locks = PyMem_Calloc(num_locks, sizeof(*config.locks));

if (config.locks == NULL) {

PyErr_NoMemory();

goto exit;

}

thread_data = PyMem_Calloc(num_threads, sizeof(*thread_data));

if (thread_data == NULL) {

PyErr_NoMemory();

goto exit;

}

thread_iters = PyList_New(num_threads);

if (thread_iters == NULL) {

goto exit;

}

PyTime_t start, end;

if (PyTime_PerfCounter(&start) < 0) {

goto exit;

}

for (Py_ssize_t i = 0; i < num_threads; i++) {

thread_data[i].config = &config;

thread_data[i].lock = &config.locks[i % num_locks];

thread_data[i].rng_state = (uint64_t)i + 1;

PyThread_start_new_thread(thread_benchmark_locks, &thread_data[i]);

}

if (total_iters == 0) {

pysleep(time_ms);

_Py_atomic_store_int(&config.stop, 1);

}

for (Py_ssize_t i = 0; i < num_threads; i++) {

PyEvent_Wait(&thread_data[i].done);

}

if (PyTime_PerfCounter(&end) < 0) {

goto exit;

}

Py_ssize_t sum_iters = 0;

for (Py_ssize_t i = 0; i < num_threads; i++) {

PyObject *iter = PyLong_FromSsize_t(thread_data[i].iters);

if (iter == NULL) {

goto exit;

}

PyList_SET_ITEM(thread_iters, i, iter);

sum_iters += thread_data[i].iters;

}

assert(end != start);

PyTime_t elapsed_ns = end - start;

double rate = sum_iters * 1e9 / elapsed_ns;

res = Py_BuildValue("(dOL)", rate, thread_iters,

(long long)elapsed_ns);

exit:

PyMem_Free(config.locks);

PyMem_Free(thread_data);

Py_XDECREF(thread_iters);

return res;

}

static PyObject *

test_lock_benchmark(PyObject *module, PyObject *obj)

{

// Just make sure the benchmark runs without crashing

PyObject *res = _testinternalcapi_benchmark_locks_impl(

module, 1, 1, 0, 100, 1, 0, 1, 0);

if (res == NULL) {

return NULL;

}

Py_DECREF(res);

Py_RETURN_NONE;

}

static int

init_maybe_fail(void *arg)

{

int *counter = (int *)arg;

(*counter)++;

if (*counter < 5) {

// failure

return -1;

}

assert(*counter == 5);

return 0;

}

static PyObject *

test_lock_once(PyObject *self, PyObject *obj)

{

_PyOnceFlag once = {0};

int counter = 0;

for (int i = 0; i < 10; i++) {

int res = _PyOnceFlag_CallOnce(&once, init_maybe_fail, &counter);

if (i < 4) {

assert(res == -1);

}

else {

assert(res == 0);

assert(counter == 5);

}

Py_RETURN_NONE;

}

struct test_rwlock_data {

Py_ssize_t nthreads;

_PyRWMutex rw;

PyEvent step1;

PyEvent step2;

PyEvent step3;

PyEvent done;

};

static void

rdlock_thread(void *arg)

{

struct test_rwlock_data *test_data = arg;

// Acquire the lock in read mode

_PyRWMutex_RLock(&test_data->rw);

PyEvent_Wait(&test_data->step1);

_PyRWMutex_RUnlock(&test_data->rw);

_PyRWMutex_RLock(&test_data->rw);

PyEvent_Wait(&test_data->step3);

_PyRWMutex_RUnlock(&test_data->rw);

if (_Py_atomic_add_ssize(&test_data->nthreads, -1) == 1) {

_PyEvent_Notify(&test_data->done);

}

static void

wrlock_thread(void *arg)

{

struct test_rwlock_data *test_data = arg;

// First acquire the lock in write mode

_PyRWMutex_Lock(&test_data->rw);

PyEvent_Wait(&test_data->step2);

_PyRWMutex_Unlock(&test_data->rw);

if (_Py_atomic_add_ssize(&test_data->nthreads, -1) == 1) {

_PyEvent_Notify(&test_data->done);

}

static void

wait_until(uintptr_t *ptr, uintptr_t value)

{

// wait up to two seconds for *ptr == value

int iters = 0;

uintptr_t bits;

do {

pysleep(10);

bits = _Py_atomic_load_uintptr(ptr);

iters++;

} while (bits != value && iters < 200);

}

static PyObject *

test_lock_rwlock(PyObject *self, PyObject *obj)

{

struct test_rwlock_data test_data = {.nthreads = 3};

_PyRWMutex_Lock(&test_data.rw);

assert(test_data.rw.bits == 1);

_PyRWMutex_Unlock(&test_data.rw);

assert(test_data.rw.bits == 0);

// Start two readers

PyThread_start_new_thread(rdlock_thread, &test_data);

// wait up to two seconds for the threads to attempt to read-lock "rw"

wait_until(&test_data.rw.bits, 8);

assert(test_data.rw.bits == 8);

// start writer (while readers hold lock)

PyThread_start_new_thread(wrlock_thread, &test_data);

wait_until(&test_data.rw.bits, 10);

assert(test_data.rw.bits == 10);

// readers release lock, writer should acquire it

_PyEvent_Notify(&test_data.step1);

wait_until(&test_data.rw.bits, 3);

assert(test_data.rw.bits == 3);

// writer releases lock, readers acquire it

_PyEvent_Notify(&test_data.step2);

wait_until(&test_data.rw.bits, 8);

assert(test_data.rw.bits == 8);

// readers release lock again

_PyEvent_Notify(&test_data.step3);

wait_until(&test_data.rw.bits, 0);

assert(test_data.rw.bits == 0);

PyEvent_Wait(&test_data.done);

Py_RETURN_NONE;

}

static PyObject *

test_lock_recursive(PyObject *self, PyObject *obj)

{

_PyRecursiveMutex m = (_PyRecursiveMutex){0};

assert(!_PyRecursiveMutex_IsLockedByCurrentThread(&m));

_PyRecursiveMutex_Lock(&m);

assert(m.thread == PyThread_get_thread_ident_ex());

assert(PyMutex_IsLocked(&m.mutex));

assert(m.level == 0);

_PyRecursiveMutex_Lock(&m);

assert(m.level == 1);

_PyRecursiveMutex_Unlock(&m);

assert(m.thread == 0);

assert(!PyMutex_IsLocked(&m.mutex));

assert(m.level == 0);

Py_RETURN_NONE;

}

static PyMethodDef test_methods[] = {

{"test_lock_basic", test_lock_basic, METH_NOARGS},

{"test_lock_two_threads", test_lock_two_threads, METH_NOARGS},

{"test_lock_counter", test_lock_counter, METH_NOARGS},

{"test_lock_counter_slow", test_lock_counter_slow, METH_NOARGS},

_TESTINTERNALCAPI_BENCHMARK_LOCKS_METHODDEF

{"test_lock_benchmark", test_lock_benchmark, METH_NOARGS},

{"test_lock_once", test_lock_once, METH_NOARGS},

{"test_lock_rwlock", test_lock_rwlock, METH_NOARGS},

{"test_lock_recursive", test_lock_recursive, METH_NOARGS},

{NULL, NULL} /* sentinel */

};

int

_PyTestInternalCapi_Init_Lock(PyObject *mod)

{

if (PyModule_AddFunctions(mod, test_methods) < 0) {

return -1;

}

return 0;

}

cpython/Modules/_testinternalcapi/test_lock.c at main · python/cpython · GitHub

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