Delete TensorBoardLogger experiment before spawning the processes.

CHANGELOG.md

@@ -205,6 +205,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed `_compare_version` for python packages ([#10762](https://github.com/PyTorchLightning/pytorch-lightning/pull/10762))
 
 
+- Fixed TensorBoardLogger `SummaryWriter` not close before spawning the processes ([#10777](https://github.com/PyTorchLightning/pytorch-lightning/pull/10777))
+
+
 ## [1.5.2] - 2021-11-16
 
 ### Fixed

pytorch_lightning/plugins/training_type/ddp_spawn.py

@@ -25,6 +25,7 @@
 from torch.nn.parallel.distributed import DistributedDataParallel
 
 import pytorch_lightning as pl
+from pytorch_lightning.loggers import LoggerCollection, TensorBoardLogger
 from pytorch_lightning.overrides import LightningDistributedModule
 from pytorch_lightning.overrides.distributed import prepare_for_backward
 from pytorch_lightning.plugins.environments.cluster_environment import ClusterEnvironment
@@ -172,6 +173,7 @@ def spawn(self, function: Callable, *args: Any, return_result: bool = True, **kw
         Return:
             The output of the function of process 0.
         """
+        self._clean_logger(*args)
         os.environ["MASTER_PORT"] = str(self.cluster_environment.main_port)
         context = mp.get_context("spawn")
         return_queue = context.SimpleQueue() if return_result else None
@@ -415,3 +417,13 @@ def teardown(self) -> None:
             self.lightning_module.cpu()
             # clean up memory
             torch.cuda.empty_cache()
+
+    @staticmethod
+    def _clean_logger(*args: Any) -> None:
+        if isinstance(args[0], pl.Trainer):
+            trainer = args[0]
+            loggers = trainer._logger_iterable if isinstance(trainer.logger, LoggerCollection) else [trainer.logger]
+            for logger in loggers:
+                if isinstance(logger, TensorBoardLogger) and logger._experiment is not None:
+                    rank_zero_warn("When using `ddp_spawn`, the Tensorboard experiment should be `None`.")
+                    logger._experiment = None