[vbox-dev] vbox kernel modules cause hardlock on kernel 4.2.0-rc2

[Ramshankar]

On 07/15/2015 11:54 AM, Jon Christopherson wrote:
> It hard locks the system with the kernel opps message i posted in my 
> first post. I have to hit reset to recover from it.
>
> -Jon
>
> On 07/15/2015 04:20 AM, Ramshankar wrote:
>> On 07/14/2015 07:35 PM, Jon Christopherson wrote:
>> > I still get the same error after that commit. I am running a kernel
>> > from today's linus git repo and still receive it.
>> >
>> > -Jon
>> >
>> > _______________________________________________
>> > vbox-dev mailing list
>> > vbox-dev at virtualbox.org
>> > https://www.virtualbox.org/mailman/listinfo/vbox-dev
>>
>> By 'error' do you mean the kernel panic or some warning in dmesg?
>>
>> Regards,
>> Ram.
>>
>

I'm not sure how that is happening.

This changeset 
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=2ecd9d29abb171d6e97a4f3eb29d7456a11401b7

reverts to the old assumptions of the caller disabling preemption while 
calling preempt_notifier_register()/preempt_notifier_unregister().

We would get into the "slower" path but i don't think that should really 
cause the kernel panic like before.

We would need to call the newly introduced functions 
preempt_notifier_inc() and preempt_notifier_dec() but that should be a 
performance issue and not a fatal panic afaict unless "WARN" ends up 
panicking the system in which case it should be a different panic and 
not the original oops you posted.

Regards,
Ram,