[child2] open#2: fd=-1 errno=4(Interrupted system call) refcount=2
[parent] open#2 reaped (interrupted) -- chopen error path ran unlock+cam_periph_release with CH_FLAG_OPEN set
[parent] refcount while open#1 still parked: 2 (expect 1: acquire+hold of open#1 minus the burned ref)
[child1] open#1 returned: refcount=1 (*** expect 0 -- undercounted with ch0 OPEN ***)
[child1] after close: refcount=0 (*** expect -1: unmatched release ***)
[parent] done
EXIT=0