multicore build error (10)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 88474739 Enable optical output when bringing an interface ..
git tree: openbsd
console output: https://syzkaller.appspot.com/x/log.txt?x=12616576500000
kernel config: https://syzkaller.appspot.com/x/.config?x=bf87b6915a88cd0d
dashboard link: https://syzkaller.appspot.com/bug?extid=7767ea7ed2e6091bd190

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7767ea...@syzkaller.appspotmail.com

failed to run ["/bin/sh" "-c" "set -eux\nOVERLAY=\"/syzkaller/userspace-multicore/overlay\"\n# Cleanup in case something failed before.\ndoas umount /altroot || true\ndoas vnconfig -u vnd0 || true\n\ndoas /sbin/vnconfig vnd0 image\ndoas mount /dev/vnd0a /altroot\ndoas cp kernel /altroot/bsd\ntest -d \"$OVERLAY\" && doas cp -Rf \"$OVERLAY\"/. /altroot\ndoas umount /altroot\ndoas vnconfig -u vnd0\n"]: exit status 1

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[Anton Lindqvist]

Same error here:

+ doas umount /altroot
umount: /altroot: Device busy

Lets see if the recently added sync(8) helps.

#syz invalid