Re: mm->mmap_sem

[James Simmons <jsimmons@edgeglobal.com>]

> > Here is another question since its very expensive putting another process 
> > to sleep. If the process owns both the accel engine and framebuffer then I
> > should be able to put the process to sleep while the accel engine is
> > running? Since the process is asleep it can't acces the framebuffer but
> > the accel engine is still running on the card.    
> 
> Oh gawd...  How much does the kernel know about the accelerator?

Its a memory region thats mmap to userspace. Thats all it knows. By the
way what I suggested above would work.

> Something to consider is that the 'right' solution might be to make the
> kernel pass console handling to a user task -- have you ever considered
> that?

Uhm. No. I don't think that will work for what I want.

> >   These are mmapped regions. So locking out the kernel will not help. You
> > have to prevent userland from accessing the memory region to prevent the
> > machine from locking. 
> 
> And the performance-correct way to do this is with a cooperative lock that
> is *not part* of the mmap'd region. 

That still doesn't prevent a rogue aplication from locking the machine on
purpose. A application could just ignore the locks.


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