Comment # 1 on bug 1209529 from Larry Finger

The other Larry and I have worked on this bug for some time. It was long
suspected that there was a locking problem, but the thought of auditing the
entire code was daunting until it was discovered that there was no problem if
the host ran VB 6.1.40. It did not matter what version the guests were running.
That essentially eliminated every code part except for vboxdrv.ko. That made
the audit be tractable. There were two files and a total of 8 places where the
locking was suspect. When those places were changed, the lockups while using
7.0.6 host code were no longer observed.

The lockups were infrequent, thus it is impossible to say that we have fixed
everything, but the frequency is clearly diminished. The final patch will be
attached.