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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