Propagate information on torch_shm_manager failures to parent process (#57307)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57307
Extend the `"ERROR"` message that `torch_shm_manager` writes to the pipe when it encounters a fatal error with some extra context (specifically, the `what()` on a caught `std::exception`), allowing the parent process to gain some insight into the cause of the failure.
Also, simply return from `main()` with an error exit code when a fatal exception is caught rather than re-throwing, because re-throwing leads to premature process termination that may prevent standard output from being flushed (and therefore the parent process from being able to read the error context from the pipe).
Reviewed By: ejguan
Differential Revision: D28047916
fbshipit-source-id: d423ee8ed1b2bf7831db877e8f8515ec6d6aa169
