Re: MMIO regions

[James Simmons <jsimmons@edgeglobal.com>]

On Mon, 4 Oct 1999, Benjamin C.R. LaHaise wrote:

> On Mon, 4 Oct 1999, James Simmons wrote:
> 
> > And if the process holding the locks dies then no other process can access
> > this resource. Also if the program forgets to release the lock you end up
> > with other process never being able to access this piece of hardware.   
> 
> Eh?  That's simply not true -- it's easy enough to handle via a couple of
> different means: in the release fop or munmap which both get called on
> termination of a task.  

Which means only one application can ever have access to the MMIO. If
another process wanted it then this application would have to tell the
other appilcation hey I want it so unmap. Then the application demanding
it would then have to mmap it.  

> Or in userspace from the SIGCHLD to the parent, 

Thats assuming its always a child that has access to a MMIO region.

> or if you're really paranoid, you can save the pid in an owner field in
the
> lock and periodically check that the process is still there.
 
How would you use this method?

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