(Noob) What's the difference between task_pid(task) and new_pid?

[Luis Fernando MuÃoz MejÃas <Luis dot Fernando dot Munoz dot Mejias at cern dot ch>]

Hello, world!

I'm doing some toy SystemTap probes and I found a weird thing. I want
to log every process that is created on my system, so I wrote this
tiny probe:

************************************************************
# Provides relevant information when a process is created
probe process.create {
        printf ("Process %d spawns child %d under uid (%d:%d)\n",
                pid(), new_pid, uid(), euid());
}
************************************************************

It does what I want it to do, but after ~3 hours it crashes. Some
annoying testing gives me a very small message like this:

"failed to access to address 0xYYYYYY on kread(&(t->tgid))"

The message I write by memory, the statement causing the crash is
exactly that one.

On the other hand, the following version:

************************************************************
# Provides relevant information when a process is created
probe process.create {
        printf ("Process %d spawns a new child %d under uid (%d:%d)\n",
                tid(), task_pid(task), uid(), euid());
}
************************************************************

has been running for three days with no problems. So, what's the
difference? Is it a bug?

I'm using systemtap-0.7.2-2.el5.el5, as shipped with RHEL 5.2.

Thanks.
-- 
Luis Fernando MuÃoz MejÃas
Luis.Fernando.Munoz.Mejias@cern.ch