Summary:
Fix a race condition when we create a thread and immediately destroy
This case should be supported.
What happens is that the thread function needs the Data instance
to actually run but has no shared ownership and must rely on the
WindowsThread instance to continue existing.
To address this we change unique_ptr to shared_ptr and then
acquire an additional refcount for the threadproc which destroys it
just before the thread exit.
We choose to allocate shared_ptr instance on the heap as this allows
the original thread to continue w/o waiting for the new thread to start
running.
Closes https://github.com/facebook/rocksdb/pull/3240
Differential Revision: D6511324
Pulled By: yiwu-arbug
fbshipit-source-id: 4633ff7996daf4d287a9fe34f60c1dd28cf4ff36
fe608e32ab