Re: [Ksummit-discuss] [CORE TOPIC] stable workflow

[Theodore Ts'o <tytso@mit.edu>]

On Mon, Jul 11, 2016 at 10:30:00AM +0530, Vinod Koul wrote:
> > There are **eleven** stable or longterm trees listed on kernel.org.
> > If you are going to ask patch submitters to test on all of the stable
> > trees, that pretty much guarantees that nothing at all will be cc'ed
> > to stable.
> 
> Isn't that a part of problem as well. If I am submitting a fix,
> shouldn't I be able to backport and validate the fix on stable kernels?

You might be *able* to pay me a $1000 dollars (e.g., you have that
much in your savings account).  That doesn't mean that you *will*, or
that you *should*, or have any moral *obligation* to pay me $1000
dollars.  (But if you do want to write me a check, feel free....  :-)

If a developer at Facebook finds a bug, and they fix it for upstream,
they do so partially out of the goodness of their hearts, and
partially because that way they don't have to do extra work to forward
port a private patch when they move to a newer upstream kernel.  But
the GPL doesn't require that they share bug fixes with upstream ---
it's just in their economic incentive to do so.  (Even if it does help
their competitors who might now not have to do the same bug report.
And since developers at Google are also doing the same thing, it all
works well.)

Ok, now let's grant that the same Facebook developer is *able* to
backport the same patch to 11 different stable kernels, and do a full
QA validation on all of these different stable.  Now the extra 15-30
minutes that it might take to prepare the patch for upstream might now
take a day or two.  What benefit does the Facebook developer have
doing that?  Almost none.  By what moral or legal right do you have to
demand that the Facebook developer do all of that extra work?  Exactly
zero.

Now, suppose *you* are under a tight deadline to get work done for
your company's shipping product.  How do you think your manager would
react if you tell her, I'm sorry, but our competitors at Qualcomm are
demanding that I take my upstream patch contribution and backport and
QA it on a dozen different stable kernels so they can more easily put
out BSP kernels for products that directly complete with Intel's?  Let
me guess that the answer might very well be, "not well".

> > And if device kernels or BSP kernels aren't bothering to track
> > -stable, it becomes even more unfair to force that work on the
> > maintainers or patch submitters.  If they are just going to be cherry
> > picking random patches out of the -stable kernel when they notice a
> > problem, does it make sense to do invest in doing full QA's for every
> > single commit before it goes into -stable?
> 
> And IMO since submitter know the target and has the hardware for test,
> it would be more easy for that person to verify..

The submitter is not necessarily going to have all of the hardware to
test.  Heck, Intel has shipped i915 drivers that have broken my
Thinkpad dock (in fact the video out on my dock has been mostly
useless for the past year), multiple times in the past and so I'm
pretty sure Intel isn't testing their i915 driver on all of the
different hardware connected to the i915 chipset --- and this is
regressions on the *HEAD* of the Linux tree, never mind backports into
stable....

       	      	    	  	     	       - Ted