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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Message-ID: <20180503132800.GH18390@sasha-vm>
Date:   Thu, 3 May 2018 13:28:04 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     Pavel Machek <pavel@....cz>
CC:     "jacek.anaszewski@...il.com" <jacek.anaszewski@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, Jan Kara <jack@...e.cz>,
        Steven Rostedt <rostedt@...dmis.org>,
        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>,
        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 Thu, May 03, 2018 at 11:36:51AM +0200, Pavel Machek wrote:
>On Tue 2018-04-17 16:19:35, Sasha Levin wrote:
>> On Tue, Apr 17, 2018 at 05:55:49PM +0200, Jan Kara wrote:
>> >On Tue 17-04-18 13:31:51, Sasha Levin wrote:
>> >> We may be able to guesstimate the 'regression chance', but there's no
>> >> way we can guess the 'annoyance' once. There are so many different use
>> >> cases that we just can't even guess how many people would get "annoyed"
>> >> by something.
>> >
>> >As a maintainer, I hope I have reasonable idea what are common use cases
>> >for my subsystem. Those I cater to when estimating 'annoyance'. Sure I don't
>> >know all of the use cases so people doing unusual stuff hit more bugs and
>> >have to report them to get fixes included in -stable. But for me this is a
>> >preferable tradeoff over the risk of regression so this is the rule I use
>> >when tagging for stable. Now I'm not a -stable maintainer and I fully agree
>> >with "those who do the work decide" principle so pick whatever patches you
>> >think are appropriate, I just wanted explain why I don't think more patches
>> >in stable are necessarily good.
>>
>> The AUTOSEL story is different for subsystems that don't do -stable, and
>> subsystems that are actually doing the work (like yourself).
>>
>> I'm not trying to override active maintainers, I'm trying to help them
>> make decisions.
>
>Ok, cool. Can you exclude LED subsystem, Hibernation and Nokia N900
>stuff from autosel work?

Curiousity got me, and I had to see what these subsystems do as far as
stable commits:

$ git log --oneline --grep 'stable@...r' --since="01-01-2016" kernel/power drivers/leds drivers/media/i2c/et8ek8 drivers/media/i2c/ad5820.c arch/x86/kernel/acpi/ | wc -l
7

Which got me a bit surprised: maybe indeed leds is mostly fine, but
hibernation is definitely tricky, I've been stung by it a few times...

So why not pick something an actual user reported, and see how that was
dealt with?

Googling first showed this:

	https://bugzilla.kernel.org/show_bug.cgi?id=97201

Which was fixed by:

	https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bdbc98abb3aa323f6323b11db39c740e6f8fc5b1

But that's not in any -stable tree. Hmm.. ok..

Next one on google was:

	https://bugzilla.kernel.org/show_bug.cgi?id=117971

Which, in turn, was fixed by:

	https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5b3f249c94ce1f46bacd9814385b0ee2d1ae52f3

Oh look at that, it's not in -stable either...

So seeing how you have concerns with my selection of -stable commits,
maybe you could explain to me why these commits didn't end up in
-stable?