Re: Ftrace and Systemtap

[Masami Hiramatsu <mhiramat at redhat dot com>]

Frank Ch. Eigler wrote:
> 
> Masami Hiramatsu <mhiramat@redhat.com> writes:
> 
>>> I always hear complaints which systemtap can't be used for the latest
>>> developing kernel. And yes, that's true.
>>
>> It will happen on a personal development branch. (note that
>> all developments are started on a personal branch :))
>> Not(or rarely) on public linus/linux-next tree.
>>
>> If someone changes some APIs which  systemtap depends on,
>> systemtap can't work on his kernel.
>> e.g. just removing EXPORT_SYMBOL_GPL(register_kprobe).
>>
>> This also shows why the out-of-tree driver is so fragile.
> 
> In theory, that makes a lot of sense.
> 
> But you made it sound like in practice it is problematic ("That is
> true.").  Please provide some substantiation of this, for anecdotes
> are all I've heard lately.  What versions have not worked / when / for
> how long?  Who has removed EXPORT_SYMBOL* something essential to
> systemtap (which by the way kprobes aren't)?

Ah, sorry about confusion. I just said that kernel developer's
complaint is true just from their viewpoint.

> I always hear complaints which systemtap can't be used for the latest
> developing kernel. And yes, that's possible.


And indeed, I haven't had any actual problem. It just be possible
to happen (so, the possibility is true.) And if it happened, I guess,
active kernel developers may not want to fix and re-install systemtap
just for catching up their changes.


Thank you,

-- 
Masami Hiramatsu
e-mail: mhiramat@redhat.com