When a7 curl calls dns_query via usrsock, it will wait a usrsock
response with the dns lock held. If a7 rptun recv a dns_addnameserver
event from another core at this time, rptun waits the lock held by
curl in callback. Then curl will never get its usrsock response with
rptun blocked, so the deadlock occurs.
This change will break lock when do usrsock request.
Signed-off-by: zhanghongyu <zhanghongyu@xiaomi.com>
db4840564d