Re: [Ksummit-2013-discuss] When to push bug fixes to mainline

[David Lang]

On Tue, 16 Jul 2013, H. Peter Anvin wrote:

> On 07/16/2013 12:19 AM, David Lang wrote:
> > On Fri, 12 Jul 2013, Willy Tarreau wrote:
> >
> > > And maybe in the end, having 1/10 patch cause a regression is not *that*
> > > dramatic, and probably less than not fixing the 9 other bugs. In one case
> > > we rely on -stable to merge the 10 fixes, and on the other case we'd rely
> > > on -stable to just revert one of them.
> >
> > Apologies for the late post, I'm catching up on things, but this jumped
> > out at me.
> >
> > We went through a LOT of pain several years ago when people got into the
> > mindset that a patch was acceptable if it fixed more people than it
> > broke. eliminating that mindset did wonders for kernel stability.
> >
> > Regressions are a lot more of a negative than bugfixes are a positive, a
> > 10:1 ratio of fixes to regressions is _not_ good enough.
>
> In my opinion, there is one exception, and that is when the problem
> being fixed is much more severe than the fix.  *In particular* two
> cases: permanently damaging hardware and corrupting data.  For example:
> no boot, as severe as it is, is much better than either of these two
> scenarios.

True, but the key point of this subthread is that regressions are _really_ bad, 
and in practice it's impossible to do enough testing to guarantee that there 
aren't regressions.

as a result, you should only risk regressions if the problem that is being fixed 
is really important. Just because someone found a bug doesn't make it important 
enough to risk regressions over.

David Lang
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