Re: Simple(?) question

[David Smith <dsmith at redhat dot com>]

Alan D. Brunelle wrote:
> I'm trying to analyze something on RHEL5 GA (errata kernel), and I'm 
> having problems getting a simple piece of histogram code to work. The 
> following compiles & runs:
>
> %{
> #include <linux/blkdev.h>
> %}
> global rd_hist
>
> probe kernel.function("__generic_unplug_device") {
>        rd_hist <<< $q->rq.count[READ]
> }

...

> semantic error: unsupported type tag 19: identifier '$q' at 
> adb-timo-hist.stp:7:14
> semantic error: probe_1462 with invalid type long for operator '.' at 
> adb-timo-hist.stp:7:20

Strangely enough I was looking into this area of systemtap on Friday, 
and I decided I didn't like those error messages.  So, I worked on 
improving them a bit.  Here's what the new messages will look like for 
your original code when I check my changes in:

====
semantic error: struct/union 'rq' is being accessed instead of a member 
of the struct/union: identifier '$q' at ../struct3.stp:3:23
semantic error: probe_1525 uses invalid operator '.' at ../struct3.stp:3:29
====

--
David Smith
dsmith@redhat.com
Red Hat
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