Hi all, this is a 486 system running 4.7.0-RELEASE and my PPPoE-gateway to the internet. It runs fine and stable all the time, except when I download the filesystem-dumps to my other machine where the tape is attached. Then after an hour or two of downloading (slow old tape) the kernel panics from rsh. The kernel debugger then always shows the following stacktrace: m_copym, tcp_output, tcp_usr_send, sosend, soo_write, dofilewrite, write, syscall2. I tried to activate INVARIANTS to see what might go wrong in m_copym(), but that doesnt work: the kernel would not even boot, but panics when attaching the devices. So I did activate INVARIANT_SUPPORT only, and defined INVARIANTS only in kern/uipc_mbuf.c (where m_copym() dwells). Now again I get the panics in the expected situation, beforehand there is a message "panic: freeing free mbuf", but the stacktrace is now totally different (and much longer), and the system cannot write a dump: it waits a while, then reports that it cannot synchronize the cache, tries to dump, then reports i/o error. I have currently no clue on how to investigate further. Ideas are welcome. rgds, Peter