def _worker_loop(dataset_kind, dataset, index_queue, data_queue, done_event,
auto_collation, collate_fn, drop_last, seed, init_fn,
worker_id, num_workers):
# See NOTE [ Data Loader Multiprocessing Shutdown Logic ] for details on the
# logic of this function.
try:
# Initialize C side signal handlers for SIGBUS and SIGSEGV. Python signal
# module's handlers are executed after Python returns from C low-level
# handlers, likely when the same fatal signal had already happened
# again.
# https://docs.python.org/3/library/signal.html#execution-of-python-signal-handlers
signal_handling._set_worker_signal_handlers()
torch.set_num_threads(1)
random.seed(seed)
torch.manual_seed(seed)
global _worker_info
_worker_info = WorkerInfo(id=worker_id,
num_workers=num_workers,
seed=seed,
dataset=dataset)
from torch.utils.data import _DatasetKind
init_exception = None
try:
if init_fn is not None:
init_fn(worker_id)
fetcher = _DatasetKind.create_fetcher(dataset_kind, dataset,
auto_collation, collate_fn,
drop_last)
except Exception:
init_exception = ExceptionWrapper(
where="in DataLoader worker process {}".format(worker_id))
# When using Iterable mode, some worker can exit earlier than others due
# to the IterableDataset behaving differently for different workers.
# When such things happen, an `_IterableDatasetStopIteration` object is
# sent over to the main process with the ID of this worker, so that the
# main process won't send more tasks to this worker, and will send
# `None` to this worker to properly exit it.
#
# Note that we cannot set `done_event` from a worker as it is shared
# among all processes. Instead, we set the `iteration_end` flag to
# signify that the iterator is exhausted. When either `done_event` or
# `iteration_end` is set, we skip all processing step and just wait for
# `None`.
iteration_end = False
watchdog = ManagerWatchdog()
while watchdog.is_alive():
try:
r = index_queue.get(timeout=MP_STATUS_CHECK_INTERVAL)
except queue.Empty:
continue
if r is None:
# Received the final signal
assert done_event.is_set() or iteration_end
break
elif done_event.is_set() or iteration_end:
# `done_event` is set. But I haven't received the final signal
# (None) yet. I will keep continuing until get it, and skip the
# processing steps.
continue
idx, index = r
if init_exception is not None:
data = init_exception
init_exception = None
else:
try:
data = fetcher.fetch(index)
except Exception as e:
if isinstance(e, StopIteration
) and dataset_kind == _DatasetKind.Iterable:
data = _IterableDatasetStopIteration(worker_id)
# Set `iteration_end`
# (1) to save future `next(...)` calls, and
# (2) to avoid sending multiple `_IterableDatasetStopIteration`s.
iteration_end = True
else:
# It is important that we don't store exc_info in a variable.
# `ExceptionWrapper` does the correct thing.
# See NOTE [ Python Traceback Reference Cycle Problem ]
data = ExceptionWrapper(
where="in DataLoader worker process {}".format(
worker_id))
data_queue.put((idx, data))
del data, idx, index, r # save memory
except KeyboardInterrupt:
# Main process will raise KeyboardInterrupt anyways.
pass
if done_event.is_set():
data_queue.cancel_join_thread()
data_queue.close()
def _worker_loop(
dataset_kind,
dataset,
index_queue,
data_queue,
done_event,
auto_collation,
collate_fn,
drop_last,
seed,
init_fn,
worker_id,
num_workers,
persistent_workers,
):
try:
# Initialize C side signal handlers for SIGBUS and SIGSEGV. Python signal # NOQA
# module's handlers are executed after Python returns from C low-level # NOQA
# handlers, likely when the same fatal signal had already happened # NOQA
# again.
# https://docs.python.org/3/library/signal.html#execution-of-python-signal-handlers # NOQA
signal_handling._set_worker_signal_handlers()
torch.set_num_threads(1)
random.seed(seed)
torch.manual_seed(seed)
global _worker_info
_worker_info = WorkerInfo(
id=worker_id, num_workers=num_workers, seed=seed, dataset=dataset
)
from torch.utils.data import _DatasetKind
init_exception = None
try:
if init_fn is not None:
init_fn(worker_id)
fetcher = _DatasetKind.create_fetcher(
dataset_kind, dataset, auto_collation, collate_fn, drop_last
)
except Exception:
init_exception = ExceptionWrapper(
where="in DataLoader worker process {}".format(worker_id)
)
iteration_end = False
watchdog = ManagerWatchdog()
while watchdog.is_alive():
try:
r = index_queue.get(timeout=MP_STATUS_CHECK_INTERVAL)
except queue.Empty:
continue
if isinstance(r, _ResumeIteration):
iteration_end = False
# Recreate the fetcher for worker-reuse policy
fetcher = _DatasetKind.create_fetcher(
dataset_kind,
dataset,
auto_collation,
collate_fn,
drop_last,
)
continue
elif r is None:
# Received the final signal
assert done_event.is_set() or iteration_end
if done_event.is_set() or (
iteration_end and not persistent_workers
):
break
continue
elif done_event.is_set() or iteration_end:
# `done_event` is set. But I haven't received the final signal
# (None) yet. I will keep continuing until get it, and skip the
# processing steps.
continue
idx, index = r
if init_exception is not None:
data = init_exception
init_exception = None
else:
try:
data = fetcher.fetch(index)
except Exception as e:
if (
isinstance(e, StopIteration)
and dataset_kind == _DatasetKind.Iterable
):
data = _IterableDatasetStopIteration(worker_id)
iteration_end = True
else:
data = ExceptionWrapper(
where="in DataLoader worker process {}".format(
worker_id
)
)
data_queue.put((idx, data))
del data, idx, index, r # save memory
except KeyboardInterrupt:
# Main process will raise KeyboardInterrupt anyways.
pass
if done_event.is_set():
data_queue.cancel_join_thread()
data_queue.close()
