>
> Marko Rauhamaa <[EMAIL PROTECTED]> writes:
>
> > > X is a user space process, thus cannot disable interrupts, and
> > > therefore cannot block the system.
>
> This is not true. X is a user space processes, but it is possible for
> user space processes to disable interrupts. I have personally done
> it. You have to modify your iopl and you have to be a supervisor
> process, but you can do it. And some X servers do this, I'm pretty
> sure. I know they go directly to the hardware.
>
> And since X directly calls the cli and sti instructions instead of
> calling the Linux functions in the kernel, even RTLinux cannot stop
> this.
>
Isn't it irq disabling via I/O to the irq controler? I would
be surprised that the X servers disable some irq other than the video ones...
I *-rgreped the Xfree86 sources: no cli.
Besides, in the ppc, the only way to disable irq is by modifying the MSR, the
only way to become supervisor (and be allowed to modify the MSR) is via
an exception (or trap, interrupt etc...). Is there another way
to become supervisor with the pentium?
Pierre Vandwalle
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