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<p>+1 to what Chandler and Reid said</p>
<div class="moz-cite-prefix">On 2/20/19 2:11 AM, Chandler Carruth
via llvm-dev wrote:<br>
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cite="mid:CAAwGriHMi_XyGUKN_2qKPv9QRTu=1jpwYDr_G0HqG3sUeavFGQ@mail.gmail.com">
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<div dir="ltr">On Tue, Feb 19, 2019 at 1:29 PM Reid Kleckner via
llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org"
moz-do-not-send="true">llvm-dev@lists.llvm.org</a>>
wrote:<br>
</div>
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<div dir="ltr">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.
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>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.</div>
</div>
</blockquote>
<div><br>
</div>
<div>I really strongly endorse this approach. This, IMO, is
the crux of revert-to-green: somewhat regardless of the
source of green vs. red, we need to revert quickly and with
relatively low bar. The result of a revert is a shared
obligation between reverter and author to find a path
forward and Reid nicely outlines how the reverter can
address their end of the bargain.</div>
<div><br>
</div>
<div>I want to emphasize that "quickly" here often (but
definitely not always) needs to be much shorter than "a few
days" or even "a day" due to the rate of incoming patches
and the need to minimize compound failures hiding precise
regression signal.</div>
<div><br>
</div>
<div>Anyways, +1 =]</div>
<div>-Chandler</div>
<div> </div>
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<div><br>
</div>
<div>I agree with Paul that we should remove the text
about checking nightly builders. That suggestion seems a
bit dated.</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, Feb 19, 2019 at
11:22 AM Zachary Turner via llvm-dev <<a
href="mailto:llvm-dev@lists.llvm.org" target="_blank"
moz-do-not-send="true">llvm-dev@lists.llvm.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
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<div dir="ltr">Hi all,
<div><br>
</div>
<div>Over the past year or so, all of us have broken
the buildbots on many occasions. Usually we get
notified on IRC, or via an buildbot email
notification sent to everyone on the blamelist. </div>
<div>If I happen to be on IRC I'll see the
notification, but if not, the next best thing is an
email that was automatically sent to me (along with
everyone else on the blamelist) from the buildbot
with information about the failure. </div>
<div>And then finally, I'll occasionally get a
response to my commit message telling me that it's
broken, and the patch may be reverted with
information in the commit message explaining which
bot was broken and providing a link to it.</div>
<div><br>
</div>
<div>However, we have some buildbots on the public
waterfall which are specifically configured not to
send emails to people. In some cases it's because
the bots are experimental, but there are a handful
where the reasoning I've been given is that it
"wastes peoples time and contributes to build
blindness", but we are still expected to keep them
green (usually by people manually reaching out to us
when they fail, or patches getting reverted and us
getting notified of the revert). </div>
<div><br>
</div>
<div>It is this last case that I'm concerned about, as
it appears to be in direct conflict with our own
developer policy [<a
href="https://llvm.org/docs/DeveloperPolicy.html#id14"
target="_blank" moz-do-not-send="true">https://llvm.org/docs/DeveloperPolicy.html#id14</a>],
which states this </div>
<div>-----</div>
<div><span style="font-family:"Lucida
Grande","Lucida Sans
Unicode",Geneva,Verdana,sans-serif;font-size:14px">We
prefer for this to be handled before submission
but understand that it isn’t possible to test all
of this for every submission. Our build bots and
nightly testing infrastructure normally finds
these problems. A good rule of thumb is to check
the nightly testers for regressions the day after
your change. Build bots will directly email you if
a group of commits that included yours caused a
failure. You are expected to check the build bot
messages to see if they are your fault and, if so,
fix the breakage.</span><br>
</div>
<div>
<p style="margin:0.8em 0px
0.5em;font-family:"Lucida
Grande","Lucida Sans
Unicode",Geneva,Verdana,sans-serif;font-size:14px">Commits
that violate these quality standards (e.g. are
very broken) may be reverted. This is necessary
when the change blocks other developers from
making progress. The developer is welcome to
re-commit the change after the problem has been
fixed.</p>
<p style="margin:0.8em 0px
0.5em;font-family:"Lucida
Grande","Lucida Sans
Unicode",Geneva,Verdana,sans-serif;font-size:14px"><span
style="font-family:sans-serif;font-size:small">-----</span> </p>
<p style="margin:0.8em 0px 0.5em">I'm sending this
email to get a sense of the community's views on
this matter. If I'm correctly reading between the
lines in the above passage, buildbots which do not
send emails should not be subject to the
revert-to-green policy. To be honest, it's
actually not even clear from reading the above
passage where the burden of fixing a "broken"
patch on a silent buildbot lies at all - with the
patch author or with the bot maintainer.<span
style="font-family:"Lucida
Grande","Lucida Sans
Unicode",Geneva,Verdana,sans-serif;font-size:14px"><br>
</span></p>
<p style="margin:0.8em 0px 0.5em"><br>
</p>
<p style="margin:0.8em 0px 0.5em">Would anyone care
to weigh in with an unbiased opinion here?</p>
</div>
</div>
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