Re: [Ksummit-discuss] [Stable kernel] feature backporting collaboration

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

On Wed, Sep 21, 2016 at 02:58:22PM +0800, Alex Shi wrote:
> 'upstream first' is good for feature development, but isn't good for
> product. Many product guys talked to me that the non-upstream porting
> didn't cost much and not the reason to pin on some stable kernel. All of
> them said that testing and stability was the most cost part. Not only
> the regular test case, benchmarks, but also the long time using for some
> trick/corner case bugs in whole system.
> 
> I doubt the 'keep rebasing on upstream' guys have been really worked on
> product?

I've worked on product kernels for consumer, and I'm horrified by what
the cr*p drivers do to stability and testing.  It also means that I've
had to port the same feature to N different product kernels, and seen
how many bug fixes (including some security-relevant fixes) aren't
getting applied the product kernel because the SOC vendor isn't
tracking the LTS kernel.  And I've also seen engineers from other
companies ask me about bug fixes that were already fixed in the LTS
kernel.

So yes, I've seen it all, from running upstream leading edge kernels
on my laptop, to product kernels for consumer products, to enterprise
distro kernels, to data center kernels where we rebase once a year or
so --- and I certainly know what I prefer, and what results in the
highest quality kernels while still allowing for bleeding edge kernel
features that allow for competitive advantages.  (Hint: it's not the
current consumer product kernel approach.)

   	   	     	     	      	     - Ted