[LAD] Realtime threads and security

[Kjetil S. Matheussen]

Paul Davis:
>
> On Thu, Feb 17, 2011 at 4:53 PM, Robin Gareus <robin at gareus.org> wrote:
>
>>> Aside of that, what about locks? I've many times been told that one mustn't do
>>> anything that could block in a realtime thread. What are the consequences of
>>> that? Could a malicious app freeze the system by blocking in a realtime thread?
>
> it poses no risks to anything except itself if it does that. blocking
> in an RT thread matters to the thread, not to anything else.
>
> to demote RT threads that are doing too much you'd need a user-space
> watchdog like das_watchdog
>

Actually, das_watchdog is not very useful anymore after the kernel
developers implemented a scheme to avoid a process to take over
the machine. This built-in scheme is also a watchdog, but much
more fine graided than das_watchdog. And it is also (more often
than not) useless, so one has to press the reboot button anyway.

The sad thing is that this built-in watchdog in newer kernels fools
das_watchdog into thinking that the system is operational.
(@#$@#%%!#$$!!!)

I should look into it though, it might not be impossible to
tune das_watchdog to work again.