Re: stpd issues

[fche at redhat dot com (Frank Ch. Eigler)]

hunt wrote:

> [...]  The problem here is that your code probes sys_read() which is
> now used by stpd to read the output from the probes.  Each time
> sys_read() is called, jprobes prints some data and flushes it, which
> causes stpd to call sys_read(), which causes more data to be
> printed, etc.  [...]

There is naturally an activity loop involved in monitoring kernel
functions that happen to be used by the kernel monitoring
infrastructure.  However, the loop is not the nasty infinite recursion
sort.  In particular, the "... which causes stpd ..."  step is
indirect, time-wise separated from the probe event.

While the probe's trace data would include the efforts of the probe
system, it should not *exclude* others.  Nor should the system hang.
We might decide to automagically filter stpd's own activities from the
trace data, but this is an aesthetic measure that should not be
required for correctness.

- FChE