Philippe Gerum authored Nov 29, 2019 and Jan Kiszka committed Dec 02, 2019

rtdm_nrtsig_pend() is based on ipipe_post_root_work(), which keeps a
copy of every request descriptor internally until it is consumed by
the secondary mode handler. Triggering rtdm_nrtsig_pend() every time a
packet is relayed from the stack to the virtual netdev may cause such
request buffer to overflow under pressure.

To address this issue, trigger the non-rt signal from
rtnetproxy_recv() only when the proxy RX queue transitions from empty
to non-empty as a result of enqueuing the next skb. To this end,
rtskb_queue_tail_check() is introduced.

Signed-off-by: Philippe Gerum <rpm@xenomai.org>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>