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From: Shiyao Ma <i@introo.me>
Date: Fri, 31 Mar 2017 03:51:00 -0000
Message-ID: <CAJQX3DyS2inKFwJPDpQc+d4PLj+zP5fFqZDcxARy--F-C+L4tw@mail.gmail.com>
Subject: Re: Is it ok to insert a module multiple times with staprun?
To: David Smith <dsmith@redhat.com>
Cc: systemtap@sourceware.org
Content-Type: text/plain; charset=UTF-8
X-SW-Source: 2017-q1/txt/msg00183.txt.bz2

Hi,

> Really to help you further you are going to have to describe what you
> are trying to do a bit further.


My aim is to pass in some information (arguments) to the module at run
time (so in pass-5 time, not pass-[1-4]).
That rules out the first option.  stap -e "foobar".

Also, using the command line of staprun does not work here, due to the
length limitation on shell command line.

The second procfs option, on the other hand, sounds feasible.
However, I have a minor concern here.  I'd like the info passed to the
module (via procfs) be read at the very beginning, *before any
kernel.function" probe has been registered to the system.
In other words, any kernel.function probe should only be activated
after the procfs.read is done.

The closest thing I can come up in my mind is to do something like:
probe begin {
  read_the_procfs_file_and_wait()
}

That is, put the reading file stuff into the begin probe.

Possible to achieve that?


Regards.