More DTrace envy [LWN.net]

More DTrace envy

Posted Jul 3, 2008 14:33 UTC (Thu) by bcantrill (guest, #31087)
In reply to: More DTrace envy by mjw
Parent article: More DTrace envy

However pretending that legal uncertainty and explicitly distributing source code under GPL-incompatible terms aren't a (the) major issue, while claiming to want wider adoption of that code base under GNU/Linux and suggesting it isn't adopted because of NIH is just silly.

And now we have arrived at the central disconnect between us and the Linux community: we did not open source Solaris to get "wider adoption of that code base under GNU/Linux"; we open sourced Solaris because of our own business objectives, some of which I have previously described. Contrary to the beliefs of some in the GNU/Linux community, GNU/Linux and GPL are not the beginning and end of open source, and as we have explained, GPLv2 was not acceptable to us because we could not dictate licensing terms to in-kernel software writers, many of whom are 3rd parties who either will not or cannot relicense. Having an open source license that allowed for different license terms (including proprietary ones) was and is a constraint; allowing our technology to be ported to other operating systems was of secondary concern.

So there you have it: while we would welcome DTrace in Linux (and we will help and are helping those that would port it), it's not something we covet. If you want it, take it. If you don't, fine -- but know that many of your users would like to see you embrace the technology, and happen to care much more about solving their business problems than about legal arguments about why it's "impossible"...

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More DTrace envy

Posted Jul 3, 2008 17:30 UTC (Thu) by bcantrill (guest, #31087) [Link]

Brian, if you want DTrace to be part of Linux, just dual-license it. You can release your code under "CDDL or GPL" and then it can happily become part of Linux. I, for one, would welcome that.

Dual licensing is something that the OpenSolaris community is very strongly against -- in part because dual licensing creates the possibility of a license-based fork. (Which given the enmity towards both Sun and the CDDL among many in the Linux camp, seems to be a very real possibility.) And again: we don't "want" DTrace to be a part of Linux -- it's up to the Linux community to want that, just as it was up to the FreeBSD, MacOS X and QNX developer communities to want it...

More DTrace envy

Posted Jul 3, 2008 19:33 UTC (Thu) by bronson (subscriber, #4806) [Link]

FreeBSD, MacOS X, QNX...  So all we have to do is relicense the Linux kernel under BSD?  Well,
why didn't you say so!  That sounds so easy!

Perhaps you're interpreting a specific licensing incompatibility as a lack of desire from the
Linux community?  I can assure you, the community as a whole really does want to integrate
DTrace.  A lot!  TONS.  It would happen in a matter of weeks if only the licenses allowed it
to be possible.

More DTrace envy

Posted Jul 3, 2008 20:00 UTC (Thu) by bcantrill (guest, #31087) [Link]

Now there's some big talk!  Do you have any idea of the technical details involved in this, or
are you one of the ESR groupies who believes that given "enough eyeballs" pixies and fairies
magically solve all problems?  I can assure you from working with Paul that the Linux
idiosyncrasies are making the DTrace port rougher going than most -- and porting DTrace is a
deeply technical endeavor on the best of days.  So it would not show up in a "matter of
weeks", even if it were GPLv2 and Torvalds himself were doing the port.  (Sacrilege, I know.)

More DTrace envy

Posted Jul 3, 2008 21:16 UTC (Thu) by bronson (subscriber, #4806) [Link]

I was careless and I'm sure you're right.  What I *should* have said is, "lots of Linux devs
would spend a lot of their time incorporating DTrace, if only the licenses allowed it."

But my point remains: you seem to be interpreting license problems as a lack of desire.  The
desire is there, no question!  If the licensing problems could just be fixed somehow, I'm
confident the Linux camp would devote amazing hours to DTrace.

As it is, they have to devote amazing hours to replicating DTrace.  :(

More DTrace envy

Posted Jul 3, 2008 19:42 UTC (Thu) by k8to (subscriber, #15413) [Link]

Wow, more disingenouousness.  I'm impressed.

More DTrace envy

Posted Jul 4, 2008 9:33 UTC (Fri) by dark (subscriber, #8483) [Link]

Dual licensing is something that the OpenSolaris community is very strongly against -- in part because dual licensing creates the possibility of a license-based fork.

No, it doesn't. Even if there were a GPL-only fork, SUN could simply use the GPL code in its CDDL products, under the "legal arguments don't matter" approach that you advocate. After all, they are both free software licenses.

Or does the shoe pinch on the other foot?

More DTrace envy

Posted Jul 6, 2008 2:13 UTC (Sun) by dirtyepic (subscriber, #30178) [Link]

Dual licensing is something that the OpenSolaris community is very strongly against -- in part because dual licensing creates the possibility of a license-based fork.

How can you fear a licensed-based fork when incompatible licenses are a "moot, philosophical matter"?

fork fears could be worked out

Posted Jul 7, 2008 18:09 UTC (Mon) by JoeBuck (subscriber, #2330) [Link]

The issue of a fork could be worked out. Sun count agree to dual-license DTrace, and Linus and the other kernel developers could agree to dual-license all improvements to that code that are accepted into the internal tree. This would neutralize any legitimate fears on the part of OpenSolaris developers that the Linux side would take and not give. It might require some re-architecting to separate out common code, from code that is Solaris-specific or Linux-specific. But Sun would gain a larger developer community to help improve the code.

More DTrace envy

Posted Jul 3, 2008 16:43 UTC (Thu) by nhippi (subscriber, #34640) [Link]

> know that many of your users would like to see you embrace the technology, and happen to
care much more about solving their business problems than about legal arguments about why it's
"impossible"

It works the other way around too. Many people would like to use solaris but can't since the
drivers are missing and care more about solving their business problems than legal arguments
why it's "impossible" to solaris to copy those drivers from Linux to solaris.

And to remind you, this problem was not created by Linux community or GPLv2, but by SUN. The
more paranoid side of community believes the problem was created on purpose.

In a hindsight it might seem it's not a problem to sun's customers, since Sun is surely
capable of rewriting (who was it again calling NiH?) all drivers needed to run the Sun servers
being sold, even if there already is a working GPLv2 driver. However, even Sun systems have
these USB/PCI-express expansion slots, where many people would like to attach interesting
hardware...

choosing whether to allow dtrace integration with gnu/linux

Posted Jul 9, 2008 20:09 UTC (Wed) by mjw (subscriber, #16740) [Link]

we would welcome DTrace in Linux

You seem to flipflop a bit on the that point :) Certainly you don't have any obligation to make it possible by removing the legal uncertainty around the current dtrace CDDL license and how it interacts with the GPL. But as you can see from the discussions whenever you claim that dtrace would be better than sliced bread for integration into GNU/Linux systems (or at least so much better than what is currently only half-integrated, like Systemtap and friends), this legal uncertainty is the only real reason dtrace isn't even a choice in providing something better.

You keep claiming that there is no way to resolve the legal ambiguity without harming the OpenSolaris community. If true, then indeed dtrace will never be a choice for GNU/Linux as a whole. I am not convinced that is really impossible though. Pure GPL or LGPL is too copyleft for your taste. That can be rectified by adding an explicit exception for your use cases. This is what Sun did for OpenJDK which had the same constraints, there still was proprietary code that needed to be linked to. The other way is of course dual-licensing. Which you say you don't want because of the fear of forks. Which of course is true and could happen in theory. But Sun also did this for projects like Glassfish and NetBeans which were originally CDDL only, but are now dual licensed CDDL/GPL. So it seems at least Sun legal thinks this is an appropriate way to both protect a code base and make it more compatible with other communities. The suggestion from others to only do this if you can get some prominent figures in the community to say that they support the dual licensing and condemn single-license forks is a good suggestion. Richard Stallman did that explicitly when Mozilla dual licensed their code (see the legal FAQ Q/A 11 till 13).

Now I am not claiming that systemtap, lttng, tracepoints, markers, kprobes, utrace, uprobes, ftrace, etc. did everything so much better than dtrace. In fact you could see all the trouble they needed to go through to make their implementations as generic as possible before being (partially) accepted and integrated into mainline as an indication of the hard work that still is still ahead for dtrace to get integrated and accepted even if the legalities were cleared up. But they did make it so that eventually their code could be integrated legally into the mainline kernel and intermingled with each other to ultimately provide better, safe and powerful frameworks for observability under GNU/Linux.

It will be interesting to see how these projects morph GNU/Linux into a fully observable system such as solaris has through dtrace. It would be even more interesting if you could lift the legal uncertainties around dtrace and make it a true contender in this coopetive race towards full observability. It is your choice to make though.