Re: MMIO regions

[James Simmons <jsimmons@edgeglobal.com>]

On Mon, 4 Oct 1999, Stephen C. Tweedie wrote:

> Hi,
> 
> On Mon, 4 Oct 1999 11:52:50 -0400 (EDT), James Simmons
> <jsimmons@edgeglobal.com> said:
> 
> >> The kernel doesn't impose any limits against this.  If you want to make
> >> this impossible, then you need to add locking to the driver itself to
> >> prevent multiple processes from conflicting.
> 
> > 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.   
>
> There are any number of ways to recover from this.  SysV semaphores, for
> example, allow you to specify UNDO when you down a semaphore, and the
> semaphore will be restored automatically on process death.
> 
> --Stephen
> 

Okay. But none of this prevents a rogue app from hosing your system. Such
a process doesn't have to bother with locks or semaphores. 
 


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