When writing a floppy image, I noticed this. Since I was not using XFS, I continued using this kernel. Behavior is not present in 2.4.16/17 kernels.
The lock does not occur with a stock 2.4.18-pre6 kernel.
I'd mark this as WONTFIX because 2.4.18-pre3+mjc3 is known to corrupt XFS filesystems, etc and is thus masked out. Drobbins indicated that he will work on new ebuilds with a different patch set so I'd say 2.4.18-pre3 shouldn't be used :) I'd recommend reverting back to linux-sources-2.4.17-r1.