Subject: Data modified on freelist
To: None <current-users@NetBSD.ORG>
From: Rick Byers <>
List: current-users
Date: 05/24/1997 09:48:50
Hi All,

After upgrading a production machine from 1.2 to 1.2.1 a few days ago,
I've seen two "Data modified on freelist" errors, which I assume isn't a
good thing what so ever :)

Data modified on freelist: word 0 of object 0xf88a0d80 size 128 previous
type free (0x4b69c != 0xdeadbeef)
Data modified on freelist: word 7 of object 0xf88f2040 size 56 previous
type VM mapent (0xdeadbeff != 0xdeadbeef)

I thought maybe deadbeff was a typo in the source somewhere, but an
exhaustive grep turned up nothing.

The first message, I could ignore as a fluke.  Now that there has been
two, I'm starting to get a little concerned.  How concerned should I be
about something like this, and is there anything I can do to try to find
the problem?  I havn't noticed any other unexplained phenomena, so it
can't be too serious... Is there anything besides faulty memory, and a
bug in the kernel that could cause something to be modified on the

I think the key here is that it never happened under 1.2. 

Rick Byers                                      Internet Access Worldwide                                System Admin, Tech Support
Welland, Ontario, Canada                                    (905)714-1400