Re: [PATCH] cpumask 5/10 rewrite cpumask.h - single bitmap based implementation

Paul Jackson
2004-06-06T12:09:32Z

Rusty wrote:
> Yes, NR_CPUS needs to get to userspace somehow sanely if we want to fix
> this in general.

Are you saying that NR_CPUS is needed, or just the number of longs in a
cpumask (sizeof (cpumask_t), essentially)?

I can see where the size is needed, in order to make the system calls to
set and get masks of arbitrary size. Since these sizes are a multiple
of sizeof(long), at a minimum this means user code needs to know the
number of longs in a mask. Though the number of bytes, as in
sizeof(cpumask_t), rather than of longs, is perhaps a less surprising
interface.

I can't see where the user code cares whether NR_CPUS is 47 or 48?

Am I missing something?

I am a firm believer in passing the minimum essential information across
major boundaries. Passing too much creates maintaince problems, and
encourages misuse of information, resulting in bogus user code.

--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <pj@sgi.com> 1.650.933.1373