Looks like a typo. :)
Index: libstdc++-v3/include/std/shared_mutex =================================================================== --- libstdc++-v3/include/std/shared_mutex (revision 226840) +++ libstdc++-v3/include/std/shared_mutex (working copy) @@ -331,7 +331,7 @@ void lock() { _M_impl.lock(); } bool try_lock() { return _M_impl.try_lock(); } - void unlock() { _M_impl.try_lock(); } + void unlock() { _M_impl.unlock(); } // Shared ownership