There are two flags to request a non-blocking receive on a socket:
MSG_NBIO and MSG_DONTWAIT. They are handled a bit differently in that
soreceive_generic() and soreceive_stream() will block on the socket I/O
lock when MSG_NBIO is set, but not if MSG_DONTWAIT is set. In general,
MSG_NBIO seems to mean, "don't block if there is no data to receive" and
MSG_DONTWAIT means "don't go to sleep for any reason".
SCTP's soreceive implementation does not allow blocking on the I/O lock
if either flag is set, but this violates an assumption in
aio_process_sb(), which specifies MSG_NBIO. Change sctp_sorecvmsg() to
block on the I/O lock only if MSG_DONTWAIT is not set.
Reported by: firstname.lastname@example.org