lost_cb
perf_buffer_lost_fn lost_cb,
p.lost_cb = lost_cb;
pb->lost_cb = p->lost_cb;
if (pb->lost_cb)
pb->lost_cb(pb->ctx, cpu_buf->cpu, s->lost);
perf_buffer_sample_fn sample_cb, perf_buffer_lost_fn lost_cb, void *ctx,
perf_buffer_lost_fn lost_cb;