caffe2/core/plan_executor: add cancellation of async nets on error + propagate exceptions via std::exception_ptr for stack traces (#31966)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31966
This has three parts:
* When `--caffe2_handle_executor_threads_exceptions` is set when a parallel execution step throws an exception it can hang waiting for async nets to finish. This adds cancellation code to cancel any async nets.
* This makes the exceptions returned from parallel workers pass a std::exception_ptr so the stack trace can be recorded with folly::SmartExceptionTracer.
* Define Cancel method at NetBase level to avoid pulling in unsupported AsyncSchedulingNet for fbandroid.
Test Plan:
Added unit tests for plan_executor
buck test //caffe2/caffe2:caffe2_test_cpu
buck test //caffe2/caffe2:caffe2_test_cpu -- PlanExecutorTest --stress-runs 100
Reviewed By: boryiingsu
Differential Revision: D19320177
fbshipit-source-id: d9939fcea1317751fa3de4172dfae7f781b71b75
