local_xchg
old = local_xchg(&bb->head, head);
local_xchg(&bb->data_size,
local_xchg(&bb->data_size, 0));
perf_aux_output_end(&bts->handle, local_xchg(&bb->data_size, 0));
perf_aux_output_end(&pt->handle, local_xchg(&buf->data_size, 0));
local_xchg(&buf->data_size,
perf_aux_output_end(&pt->handle, local_xchg(&buf->data_size, 0));
#define local64_xchg(l, n) local_xchg((&(l)->a), (n))
lost_event.lost = local_xchg(&rb->lost, 0);