linux-kernel - Re: linux-next build error (8)

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Message-ID: <ef4ec876-8b78-3f4a-a3fb-6dbc038e92df@infradead.org>
Date:   Fri, 20 Mar 2020 09:34:13 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     paulmck@...nel.org, Dmitry Vyukov <dvyukov@...gle.com>
Cc:     syzbot <syzbot+792dec47d693ccdc05a0@...kaller.appspotmail.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>, rcu@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: linux-next build error (8)

On 3/20/20 9:26 AM, Paul E. McKenney wrote:
> On Fri, Mar 20, 2020 at 04:38:54PM +0100, Dmitry Vyukov wrote:
>> On Thu, Mar 19, 2020 at 4:04 PM Paul E. McKenney <paulmck@...nel.org> wrote:
>>>
>>> On Thu, Mar 19, 2020 at 08:13:35AM +0100, Dmitry Vyukov wrote:
>>>> On Wed, Mar 18, 2020 at 10:41 PM Paul E. McKenney <paulmck@...nel.org> wrote:
>>>>>
>>>>> On Wed, Mar 18, 2020 at 09:54:07PM +0100, Dmitry Vyukov wrote:
>>>>>> On Wed, Mar 18, 2020 at 5:57 PM syzbot
>>>>>> <syzbot+792dec47d693ccdc05a0@...kaller.appspotmail.com> wrote:
>>>>>>>
>>>>>>> Hello,
>>>>>>>
>>>>>>> syzbot found the following crash on:
>>>>>>>
>>>>>>> HEAD commit:    47780d78 Add linux-next specific files for 20200318
>>>>>>> git tree:       linux-next
>>>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=14228745e00000
>>>>>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=b68b7b89ad96c62a
>>>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=792dec47d693ccdc05a0
>>>>>>> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
>>>>>>>
>>>>>>> Unfortunately, I don't have any reproducer for this crash yet.
>>>>>>>
>>>>>>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>>>>>>> Reported-by: syzbot+792dec47d693ccdc05a0@...kaller.appspotmail.com
>>>>>>>
>>>>>>> kernel/rcu/tasks.h:1070:37: error: 'rcu_tasks_rude' undeclared (first use in this function); did you mean 'rcu_tasks_qs'?
>>>>>>
>>>>>> +rcu maintainers
>>>>>
>>>>> The kbuild test robot beat you to it, and apologies for the hassle.
>>>>> Fixed in -rcu on current "dev" branch.
>>>>
>>>> If the kernel dev process would only have a way to avoid dups from all
>>>> test systems...
>>>
>>> I do significant testing before pushing to -next, but triggering this
>>> one requires a combination of Kconfig options that are incompatible
>>> with rcutorture.  :-/
>>>
>>> I suppose one strategy would be to give kbuild test robot some time before
>>> passing to -next, but they seem to sometimes get too far behind for me to
>>> be willing to wait that long.  So my current approach is to push my "dev"
>>> branch, run moderate rcutorture testing (three hours per scenario other
>>> than TREE10, which gets only one hour), and if that passes, push to -next.
>>>
>>> I suppose that I could push to -next only commits that are at least three
>>> days old or some such.  But I get in trouble pushing to -next too slowly
>>> as often as I get in trouble pushing too quickly, so I suspect that my
>>> current approach is in roughly the right place.
>>>
>>>> Now we need to spend time and deal with it. What has fixed it?
>>>
>>> It is fixed by commit c6ef38e4d595 ("rcu-tasks: Add RCU tasks to
>>> rcutorture writer stall output") and some of its predecessors.
>>>
>>> Perhaps more useful to you, this commit is included in next-20200319
>>> from the -next tree.  ;-)
>>
>> Let's tell syzbot about the fix:
>>
>> #syz fix: rcu-tasks: Add RCU tasks to rcutorture writer stall output
>>
>> I think what you are doing is the best possible option in the current situation.
>> I don't think requiring all human maintainers to do more manual
>> repetitive work, which is not well defined and even without a way to
>> really require something from them is scalable nor reliable nor the
>> right approach.
> 
> Thank you, and I do greatly appreciate the automation!
> 
>> We would consume something like LKGR [1] if it existed for the kernel.
>> But it would require tighter integration of testing systems with
>> kernel dev processes, or of course throwing more manual labor at it to
>> track all uncoordinated testing systems and publishing LKGR tags.
>>
>> [1] https://chromium.googlesource.com/chromiumos/docs/+/master/glossary.md
> 
> At my end, it is pretty quick and easy to detect duplicate notifications
> of the same bug, so the current situation isn't causing me undue distress.

Yeah, I saw the same build error and did-not-report it since it was
already reported.  :)

-- 
~Randy