Re: AAARGH bisection is hard (Re: [2.6.39 regression] X locks uphard right after logging in)

From: Junio C Hamano
Date: Fri May 13 2011 - 14:49:22 EST


Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> writes:

> When you say that v2.6.38 is good, that means that everything that can
> be reached from 2.6.38 is good.
>
> NOT AT ALL the same thing as "git bisect requires v2.6.38" would be.
>
> The "requires v2.6.38" would basically say that anything that doesn't
> contain v2.6.38 is "off-limits". It's fine to call them "good", but
> that's not the same thing as "git bisect good v2.6.38".
>
> Why?
>
> Think about it. It's the "reachable from v2.6.38" vs "cannot reach
> v2.6.38" difference. That's a HUGE difference.

Could you please clarify "off-limits"?

Do you mean "anything before v2.6.38 did not even have this feature, so
the result of testing a version in that range does not give us any
information"? The feature didn't even exist, so a bug can never trigger,
and seeing "good" from such a version does not mean everything reachable
from it is good? Upon seeing "bad" result from a version before v2.6.38,
what can we conclude? The breakage cannot possibly come from the feature
that is being checked, so the procedure to check itself is busted?


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