linux-kernel - Re: [PATCH AUTOSEL for 4.14 015/161] printk: Add console owner and waiter logic to load balance console writes

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Date:   Mon, 16 Apr 2018 16:53:00 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     Steven Rostedt <rostedt@...dmis.org>
CC:     Pavel Machek <pavel@....cz>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Petr Mladek <pmladek@...e.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Peter Zijlstra <peterz@...radead.org>, Jan Kara <jack@...e.cz>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Byungchul Park <byungchul.park@....com>,
        Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH AUTOSEL for 4.14 015/161] printk: Add console owner and
 waiter logic to load balance console writes

On Mon, Apr 16, 2018 at 12:47:11PM -0400, Steven Rostedt wrote:
>On Mon, 16 Apr 2018 16:31:09 +0000
>Sasha Levin <Alexander.Levin@...rosoft.com> wrote:
>
>> On Mon, Apr 16, 2018 at 12:22:44PM -0400, Steven Rostedt wrote:
>> >On Mon, 16 Apr 2018 16:14:15 +0000
>> >Sasha Levin <Alexander.Levin@...rosoft.com> wrote:
>> >
>> >> Since the rate we're seeing now with AUTOSEL is similar to what we were
>> >> seeing before AUTOSEL, what's the problem it's causing?
>> >
>> >Does that mean we just doubled the rate of regressions? That's the
>> >problem.
>>
>> No, the rate stayed the same :)
>>
>> If before ~2% of stable commits were buggy, this is still the case with
>> AUTOSEL.
>
>Sorry, I didn't mean "rate" I meant "number". If the rate stayed the
>same, that means the number increased.

Indeed, just like the number of regressions in mainline has increased
over time.

>>
>> >>
>> >> How do you know if a bug bothers someone?
>> >>
>> >> If a user is annoyed by a LED issue, is he expected to triage the bug,
>> >> report it on LKML and patiently wait for the appropriate patch to be
>> >> backported?
>> >
>> >Yes.
>>
>> I'm honestly not sure how to respond.
>>
>> Let me ask my wife (who is happy using Linux as a regular desktop user)
>> how comfortable she would be with triaging kernel bugs...
>
>That's really up to the distribution, not the main kernel stable. Does
>she download and compile the kernels herself? Does she use LEDs?
>
>The point is, stable is to keep what was working continued working.
>If we don't care about introducing a regression, and just want to keep
>regressions the same as mainline, why not just go to mainline? That way
>you can also get the new features? Mainline already has the mantra to
>not break user space. When I work on new features, I sometimes stumble
>on bugs with the current features. And some of those fixes require a
>rewrite. It was "good enough" before, but every so often could cause a
>bug that the new feature would trigger more often. Do we back port that
>rewrite? Do we backport fixes to old code that are more likely to be
>triggered by new features?
>
>Ideally, we should be working on getting to no regressions to stable.

This is exactly what we're doing.

If a fix for a bug in -stable introduces a different regression,
should we take it or not?