4.3.20 almost hung guest? (host win7 64-bit, guest Debian GNU/Linux 64-bit)

[ci-zephyurus]

I have upgraded to 4.3.20 some time ago.

Since then, I have experienced the following problems several times. Host Windows 7 64-bit. Guest Debian GNU/Linux 64-bit.

The guest seems to hung almost:

• I say "almost" because, most of the time when this happens, the cursor seems to be working, i.e., I can move the cursor over the vbox screen area and it changes shape. So it means probably the vbox guest driver for X is working (?)

• However, there *ARE* times, even the mouse doesn't appear and Vbox itself seems to get hung :-( This is rare but it does happen.

I searched the bugtracker but could not find similar issues.

Seen from the windows side when the problems occurred, sometimes VBox seems to be spinning on something and uses two cores assinged to it almost 100 %. Other times, it does not seem to use much CPU time. Very random.

I am attaching a log when I had to power-reset the guest because it almost gets hung (again, the mouse cursor seems to be alive) so at least Vbox itself is alive, etc. I tried APCI reset, and then to my surprise, Debian GNU/Linux's panel for logout/shutdown, etc appears, but I cannot push any of the button although the cursor moves. Anyway, I am attaching Vbox.log when this happened. Oh, one more thing, when I tried to continue after [POWER RESET] during booting of Debian GNU/Linux from grub, the VBox itself became unresponsive, and I had to kill it by hitting [x] button on the upper right corner. (To be honest I forgot if I did this, or I killed it from task manager.) Anyway, Vbox.log *may* contain something there.

I am afraid that the symptom seems to happen when I invoke heavy I/O, but not sure exactly when this happens. Since my PC has ECC memory I would like to rule out hardware problems, but who knows. The particular Vbox.log was created after I was disconnecting and connecting VBox network adaptor a few times to try to simulate network problems and when I was testing the behavior of the program, the problem struck.

But other problems occurred without network adaptor removal, etc.

TIA

[ci-zephyurus]

When the quasi guest hung occurred, and the subsequent boot after power reset failed.

[aeichner]

Please reopen if still relevant with a recent VirtualBox release.