Use static FOLLY_TLS ThreadEntry to avoid an ASAN deadlock due to new after fork

Summary: Use static FOLLY_TLS ThreadEntry to avoid an ASAN deadlock due to new after fork

Reviewed By: philippv

Differential Revision: D8272580

fbshipit-source-id: e2dc069e81d15f14be9f96a26d30de7482ced0cf

folly/detail/ThreadLocalDetail.cpp

@@ -183,7 +183,9 @@ void StaticMetaBase::onThreadExit(void* ptr) {
       tmp->elementsCapacity = 0;
     }
 
+#ifndef FOLLY_TLD_USE_FOLLY_TLS
     delete tmp;
+#endif
   }
 
 #ifndef FOLLY_TLD_USE_FOLLY_TLS

folly/detail/ThreadLocalDetail.h

@@ -447,8 +447,8 @@ struct StaticMeta : StaticMetaBase {
     if (!threadEntry) {
       ThreadEntryList* threadEntryList = StaticMeta::getThreadEntryList();
 #ifdef FOLLY_TLD_USE_FOLLY_TLS
-      static FOLLY_TLS ThreadEntry* one;
-      threadEntry = FOLLY_LIKELY(!!one) ? one : (one = new ThreadEntry());
+      static FOLLY_TLS ThreadEntry threadEntrySingleton;
+      threadEntry = &threadEntrySingleton;
 #else
       threadEntry = new ThreadEntry();
 #endif