Mbuf double-free guilty party detection patch

[Mike Silbersack]

On Sun, 26 Jun 2005, Thierry Herbelot wrote:

> still no good luck : after using the second patch, no panic, but the debug
> messages seem incomplete : (last freed by: /0/)
>
> This memory last freed by: 0
> Memory modified after free 0xc15d5800(256) val=800 @ 0xc15d583c
> This memory last freed by: 0
> Memory modified after free 0xc15d5800(256) val=0 @ 0xc15d5840
> This memory last freed by: 0
> Memory modified after free 0xc15d5800(256) val=3 @ 0xc15d5844

Well, since I store the address inside of the mbuf, if whatever reuses it 
zeros it out, we'll see zero. :(

Once I have memguard modified, we'll see what we can learn.

> the test case is : building the kernel while tar-ing the src tree over two
> separate ssh session.
>
> 	TfH
>
> PS : what is puzzling is that I've got another machine running a more recent
> -current, with no ill effects (but it uses an ed(4) I/F)

It'll be interesting to learn the answer. :)

Mike "Silby" Silbersack