Re: [PATCH 0/4][RFC] event tracer

[Jason Baron <jbaron@redhat.com>]

On Tue, Feb 24, 2009 at 09:10:33PM -0500, Frank Ch. Eigler wrote:
> Hi -
> 
> > This is still RFC, do not pull.
> > This patch set gives the ability to add a format string and args to
> > a trace point declaration. [...]
> 
> It looks like a good compromise, a dual to the trace_mark_tp
> prototype, and a plausible replacement for markers.  Thank you.  The
> main thing this would lose is a callback API to intercept generic
> varargs event flavour, which we in systemtap land enjoy using, but
> before too long we would make do.
> 

Along these lines, I think it should be possible to have
'DEFINE_TRACE_FMT' define an additional tracepoint with a
signature that is simply a fomat string and a list of args. This
tracpoint is then what could be registred with the original tracepoint.
Then, event_trace_printk can be registered with this additional
tracepoint. In this way different consumers would be able to register
not only with the oringal tracepoint, but also with a format string
callback version of it. this obviously adds extra functions call, but at
the advantage of additional flexibility. If ppl think this makes sense,
I can prototype a patch.

thanks,

-Jason