[llvm-dev] Clarification on expectations of buildbot email notifications

via llvm-dev llvm-dev at lists.llvm.org
Wed Feb 20 07:39:30 PST 2019

Reid said:

> I don't think whether a buildbot sends email should have anything to do
> with whether we revert to green or not. Very often, developers commit
> patches that cause regressions not caught by our buildbots. If the
> regression is severe enough, then I think community members have the
> right, and perhaps responsibility, to revert the change that caused it.
> Our team maintains bots that build chrome with trunk versions of clang,
> and we identify many regressions this way and end up doing many reverts
> as a result. I think it's important to continue this practice so that
> we don't let multiple regressions pile up.

My team also has internal bots and we see breakages way more often than
we'd like.  We are a bit reluctant to just go revert something, though,
and typically try to engage the patch author first.

Engaging the author has a couple of up-sides: it respects the author's
contribution and attention to the process; and once you've had to fix
a particular problem yourself (rather than someone else cleaning up
after your mess) you are less likely to repeat that mistake.

> I think what's important, and what we should, after this discussion
> concludes, put in the developer policy, is that the person doing the
> revert has the responsibility to do their best to help the patch author
> reproduce the problem or at least understand the bug.
> This can take many forms. They can link directly to an LLVM buildbot,
> which should be self-explanatory as far as reproduction goes. It can be
> an unreduced crash report. If they're nice, they can use CReduce to make
> it smaller. But, a reverter can't just say "Revert rNNN, breaks
> $RANDOM_PROJECT on x86_64-linux-gu". If they add, "reduction forthcoming"
> and they deliver on that promise, I think we should support that.
> In other words, the bar to revert should be low, so we can do it fast
> and save downstream consumers time and effort. If someone isn't making
> a good faith effort to follow up after a revert, then authors have a
> right to push back.

We have been on the wrong side of a revert where it was "this broke us"
and then nothing. I was inclined to just re-apply the patch, but that's
my "Mr Grumpy" avatar talking. How do we address failure to conform to the
community norms?

> I agree with Paul that we should remove the text about checking nightly
> builders. That suggestion seems a bit dated.

That was Tom Stellard, not me, but I agree with him.

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