Proposal: a revoke() system call

[Robert Watson]

On Tue, 8 Jul 2008, Ed Schouten wrote:

> I also noticed similar constructs inside the stat() calls, to translate 
> device major/minor numbers. As you can see, some stat() routines call 
> translate_path_major_minor_at() after performing the regular stat() 
> operation. The translate_path_major_minor_at() is implemented by calling 
> kern_openat(). This has three disadvantages:
>
> - It is non-atomic.
>
> - It can only perform the translation on nodes it has O_RDONLY access
>  to. This shouldn't be a big problem, but may cause inconsistencies
>  when users look around in devfs.
>
> - The translation may not always work when the calling process is out of
>  file descriptors.

- Opening a device node can have side effects, such as rewinding tapes,
   raising DTR on serial lines, triggering errors, or denying access to other
   consumers due to exclusive access requirements.

Robert N M Watson
Computer Laboratory
University of Cambridge