8000 [3.13] gh-125716: Use a Global Mutex When Initializing Global State For the _interpqueues Module by miss-islington · Pull Request #125817 · python/cpython · GitHub
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[3.13] gh-125716: Use a Global Mutex When Initializing Global State For the _interpqueues Module #125817

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Merged
merged 1 commit into from
Oct 21, 2024
Merged

[3.13] gh-125716: Use a Global Mutex When Initializing Global State For the _interpqueues Module #125817

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gh-125716: Use A Global Mutex When Initializing Global State For The … 
…_interpqueues Module (gh-125803)

This includes a drive-by cleanup in _queues_init() and _queues_fini().

This change also applies to the _interpchannels module.
(cherry picked from commit 4848b0b)

Co-authored-by: Eric Snow <ericsnowcurrently@gmail.com>
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@ericsnowcurrently @miss-islington
ericsnowcurrently authored and miss-islington committed Oct 21, 2024
commit b739d2e439f7a09ba507b6585e102d0cf1ca7089
64 changes: 39 additions & 25 deletions Modules/_interpchannelsmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@
This module has the following process-global state:

_globals (static struct globals):
mutex (PyMutex)
module_count (int)
channels (struct _channels):
numopen (int64_t)
Expand Down Expand Up @@ -1349,21 +1350,29 @@ typedef struct _channels {
static void
_channels_init(_channels *channels, PyThread_type_lock mutex)
{
channels->mutex = mutex;
channels->head = NULL;
channels->numopen = 0;
channels->next_id = 0;
assert(mutex != NULL);
assert(channels->mutex == NULL);
*channels = (_channels){
.mutex = mutex,
.head = NULL,
.numopen = 0,
.next_id = 0,
};
}

static void
_channels_fini(_channels *channels)
_channels_fini(_channels *channels, PyThread_type_lock *p_mutex)
{
PyThread_type_lock mutex = channels->mutex;
assert(mutex != NULL);

PyThread_acquire_lock(mutex, WAIT_LOCK);
assert(channels->numopen == 0);
assert(channels->head == NULL);
if (channels->mutex != NULL) {
PyThread_free_lock(channels->mutex);
channels->mutex = NULL;
}
*channels = (_channels){0};
PyThread_release_lock(mutex);

*p_mutex = mutex;
}

static int64_t
Expand Down Expand Up @@ -2812,39 +2821,44 @@ set_channelend_types(PyObject *mod, PyTypeObject *send, PyTypeObject *recv)
the data that we need to share between interpreters, so it cannot
hold PyObject values. */
static struct globals {
PyMutex mutex;
int module_count;
_channels channels;
} _globals = {0};

static int
_globals_init(void)
{
// XXX This isn't thread-safe.
PyMutex_Lock(&_globals.mutex);
assert(_globals.module_count >= 0);
_globals.module_count++;
if (_globals.module_count > 1) {
// Already initialized.
return 0;
}

assert(_globals.channels.mutex == NULL);
PyThread_type_lock mutex = PyThread_allocate_lock();
if (mutex == NULL) {
return ERR_CHANNELS_MUTEX_INIT;
if (_globals.module_count == 1) {
// Called for the first time.
PyThread_type_lock mutex = PyThread_allocate_lock();
if (mutex == NULL) {
_globals.module_count--;
PyMutex_Unlock(&_globals.mutex);
return ERR_CHANNELS_MUTEX_INIT;
}
_channels_init(&_globals.channels, mutex);
}
_channels_init(&_globals.channels, mutex);
PyMutex_Unlock(&_globals.mutex);
return 0;
}

static void
_globals_fini(void)
{
// XXX This isn't thread-safe.
PyMutex_Lock(&_globals.mutex);
assert(_globals.module_count > 0);
_globals.module_count--;
if (_globals.module_count > 0) {
return;
if (_globals.module_count == 0) {
PyThread_type_lock mutex;
_channels_fini(&_globals.channels, &mutex);
assert(mutex != NULL);
PyThread_free_lock(mutex);
}

_channels_fini(&_globals.channels);
PyMutex_Unlock(&_globals.mutex);
}

static _channels *
Expand Down
72 changes: 40 additions & 32 deletions Modules/_interpqueuesmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -845,28 +845,31 @@ typedef struct _queues {
static void
_queues_init(_queues *queues, PyThread_type_lock mutex)
{
queues->mutex = mutex;
queues->head = NULL;
queues->count = 0;
queues->next_id = 1;
assert(mutex != NULL);
assert(queues->mutex == NULL);
*queues = (_queues){
.mutex = mutex,
.head = NULL,
.count = 0,
.next_id = 1,
};
}

static void
_queues_fini(_queues *queues)
_queues_fini(_queues *queues, PyThread_type_lock *p_mutex)
{
PyThread_type_lock mutex = queues->mutex;
assert(mutex != NULL);

PyThread_acquire_lock(mutex, WAIT_LOCK);
if (queues->count > 0) {
PyThread_acquire_lock(queues->mutex, WAIT_LOCK);
assert((queues->count == 0) != (queues->head != NULL));
_queueref *head = queues->head;
queues->head = NULL;
queues->count = 0;
PyThread_release_lock(queues->mutex);
_queuerefs_clear(head);
}
if (queues->mutex != NULL) {
PyThread_free_lock(queues->mutex);
queues->mutex = NULL;
assert(queues->head != NULL);
_queuerefs_clear(queues->head);
}
*queues = (_queues){0};
PyThread_release_lock(mutex);

*p_mutex = mutex;
}

static int64_t
Expand Down Expand Up @@ -1398,39 +1401,44 @@ _queueobj_shared(PyThreadState *tstate, PyObject *queueobj,
the data that we need to share between interpreters, so it cannot
hold PyObject values. */
static struct globals {
PyMutex mutex;
int module_count;
_queues queues;
} _globals = {0};

static int
_globals_init(void)
{
// XXX This isn't thread-safe.
PyMutex_Lock(&_globals.mutex);
assert(_globals.module_count >= 0);
_globals.module_count++;
if (_globals.module_count > 1) {
// Already initialized.
return 0;
}

assert(_globals.queues.mutex == NULL);
PyThread_type_lock mutex = PyThread_allocate_lock();
if (mutex == NULL) {
return ERR_QUEUES_ALLOC;
if (_globals.module_count == 1) {
// Called for the first time.
PyThread_type_lock mutex = PyThread_allocate_lock();
if (mutex == NULL) {
_globals.module_count--;
PyMutex_Unlock(&_globals.mutex);
return ERR_QUEUES_ALLOC;
}
_queues_init(&_globals.queues, mutex);
}
_queues_init(&_globals.queues, mutex);
PyMutex_Unlock(&_globals.mutex);
return 0;
}

7830 static void
_globals_fini(void)
{
// XXX This isn't thread-safe.
PyMutex_Lock(&_globals.mutex);
assert(_globals.module_count > 0);
_globals.module_count--;
if (_globals.module_count > 0) {
return;
if (_globals.module_count == 0) {
PyThread_type_lock mutex;
_queues_fini(&_globals.queues, &mutex);
assert(mutex != NULL);
PyThread_free_lock(mutex);
}

_queues_fini(&_globals.queues);
PyMutex_Unlock(&_globals.mutex);
}

static _queues *
Expand Down
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