- SysArena zombies_; // allocated from threads that are now dead
- std::mutex zombiesMutex_;
- ThreadLocalPtr<SysArena> arena_; // per-thread arena
+
+ ThreadLocalPtr<SysArena, ThreadLocalPtrTag> arena_; // Per-thread arena.
+
+ // Allocations from threads that are now dead.
+ Synchronized<SysArena> zombies_;