Re: Proposal for new syscalls: getrusagex and waitx

[Matt Thomas <matt%3am-software.com@localhost>]

On Oct 18, 2008, at 11:10 AM, David Holland wrote:

> On Thu, Oct 16, 2008 at 10:09:39PM -0700, Matt Thomas wrote:
> > I'd to add return some additional data in getrusage or wait4.   
> > Extending
> > struct rusage seems to be a losing proposition since I will need  
> > to version
> > the syscalls and provide compatiblity shims.  I might as well just  
> > add
> > variants that return proplib dictionaries with the information.
> >
> > int getrusagex(int who, struct plistref *dict)
> > int waitx(pid_t wpid, int *status, int options, struct plistref  
> > *rusage);
>
> That should be wait5, for consistency with the various other forms of
> wait.

I use x because these are eXtensible.  No reason to version then  
futher since
the proplib can adapt.

> More importantly, however, do you expect the additional data to be of
> interest to 3rd-party callers? Because if so we'll end up doing all
> the same versioning to provide an extended struct rusage to them,
> except that it'll have to be done in libc where such versioning is
> much harder. That's not a win.

Huh?  I intend to return more statistics.  There's no reason to do  
anything
in libc.  If you want to access the new items, just grab them  
directly from
the proplib.

> It is not reasonable to expect that 3rd-party callers are going to
> wade through a proplist, especially since the existence and some of
> the contents of struct rusage are defined by the pertinent standards.

If they don't know the new information, they can continue to use the  
existing
wait4/getrusage.

> So unless what you're intending to add is of no value except to one or
> two system utilities, this doesn't seem like a good idea. (And if it
> is only of such value, it seems like there are simpler ways to
> proceed.)

I guess that depends on your definition of simpler.  Versioning  
struct rusage
seems to be as much work and then it only works once.  With a probib,  
once it's
been once it doesn't need to be done ever again.

> > As for the items I want to add, a description of those can wait  
> > for later.
>
> Well, no, I think that's pretty important, for the above reasons.

Well, I think you're reasons are for the most bogus.