error[E0499]: cannot borrow `dca` as mutable more than once at a time
  --> tests/ui/dca_dbuf_double_lend.rs:21:17
   |
18 |     let cpu_a = dca.cpu();
   |                 --- first mutable borrow occurs here
...
21 |     let cpu_b = dca.cpu();
   |                 ^^^ second mutable borrow occurs here
22 |     let _ = cpu_a.start_double_buffer_read(&mut ctx);
   |             ----- first borrow later used here
