After processing certain asynchronous requests from VFS, VM would send
an asynchronous reply without supplying the AMF_NOREPLY flag. As a
result, this asynchronous reply could be taken as the result of an
ipc_sendrec() call, causing the entire VM/VFS communication to become
desynchronized. The end result was a deadlock-induced panic during a
later request.
This bug was exposed because of the higher-than-usual concurrency
level in the NetBSD rc scripts. The fix consists of properly setting
the AMF_NOREPLY flag for asynchronous replies.