Re: tapset feedback

[Martin Hunt <hunt@redhat.com>]

On Thu, 2006-01-05 at 03:17 -0800, Roland McGrath wrote:

>  If a user script might want to use
> kernel.syscall.foobar directly, then it will have to use % conditionals to
> avoid those uses on kernels where the probe won't be defined because it
> can't work; i.e., have to know the kernel versions to test for,

This is exactly the ugly situation we now have. For every function that
gets added/removed we have to know the exact kernel versions it happened
in. And this means systemtap becomes less useful for nonstandard kernels
because we won't know what options they were built with.

>  or perhaps
> allow libraries/tapsets to export symbolic conditionals so a user can test
> with %(have_foobar) in conditionals.

That would have to be a runtime conditional.

> The other choice is to define a special notion of "never" probes.  

So the idea here is that we define for each probe what to do if the
probe does not match any current function. Isn't this kind of similar to
my (perhaps poorly named) kernel.func probe point? Using kernel.func vs
kernel.function means "do nothing if this probe point fails to match".

What I REALLY would like to see is a way to say "here is a list of probe
points. Set probes on as many as possible."

Martin