panic: Memory modified after free

[Doug White]

On Thu, 23 Oct 2003, othermark wrote:

> these are fibre 1000 base sx connections.  They don't attach correctly in
> the 5.0-release kernel as well (with the exact same error), but it does
> continue to boot correctly.  These are hardwired into the bus, and I'm
> unable to disable them. :(

Onboard fiber? What kind of system is this?

> > That or perhaps you have bad memory.  Do you have ECC RAM in the system?
>
> I'm not positive, so I'm going to say no, but I'm also fairly sure that
> the memory is good.  I ran make buildworld on 5.0 successfully w/o any
> problems.  Slow bios memcheck at startup is good.

That memcheck is useless, sadly.  You might track down a copy of memtest86
and run it on your system just to be sure. Its a much more intensive
diagnostic.

> this seems similar to:
> http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/53566
>
> except the last user is of memory is different.

I suspect the actual last user is irrelevant; its a leaking pointer
reference somewhere and the memory allocator is handing the memory block
it points to back out to some innocent bystander who triggers the panic.

> I think the next step is to move up to a 5.1-release kernel and see if
> it boots as well as the 5.0-release does, or provides a more interesting
> panic.

Have you emailed the em driver maintainer yet?

-- 
Doug White                    |  FreeBSD: The Power to Serve
dwhite at gumbysoft.com          |  www.FreeBSD.org