Summary: https://github.com/facebook/rocksdb/pull/2380 introduces a regression by replacing __thread with ThreadLocalPtr. Revert the thread local implementation back. Closes https://github.com/facebook/rocksdb/pull/2485 Differential Revision: D5308050 Pulled By: lightmark fbshipit-source-id: 2676e9c22edf76e8133d3f4c50e2711e11a95480