I've been writing a (minimal!) reproducer script that uses the same mechanisms as autopkgtest to copy files across but without any of the autopkgtest infrastructure - just host, qemu guest, and the shared 9P directory. Even with 2500 iterations of the tar-based copy of the "hello" package source and build product so far it has failed to reproduce. I intend to add lots of unique individual file copies since autopkgtest does a lot fo that prior to hitting the tar-based transfer hang.
Update: 6.10-rc2 still fails the same way.
I've been writing a (minimal!) reproducer script that uses the same mechanisms as autopkgtest to copy files across but without any of the autopkgtest infrastructure - just host, qemu guest, and the shared 9P directory. Even with 2500 iterations of the tar-based copy of the "hello" package source and build product so far it has failed to reproduce. I intend to add lots of unique individual file copies since autopkgtest does a lot fo that prior to hitting the tar-based transfer hang.