Thread 1:
static int
__log_newfile(WT_SESSION_IMPL *session, bool conn_open, bool *created)
{
    for (yield_cnt = 0; log->log_close_fh != NULL;) {} // ACQUIRE 2

    WT_ASSIGN_LSN(&log->log_close_lsn, &log->alloc_lsn);

    WT_RELEASE_WRITE_WITH_BARRIER(log->log_close_fh, log->log_fh); // RELEASE 1
}


Thread 2: 
__log_file_server(void *arg) {
    while (true) {
        WT_ACQUIRE_READ_WITH_BARRIER(close_fh, log->log_close_fh); // ACQUIRE 1
        if (close_fh != NULL) {
            WT_ASSIGN_LSN(&close_end_lsn, &log->log_close_lsn);
            WT_FULL_BARRIER();
            log->log_close_fh = NULL; // RELEASE 2
        }
    }
}