linux-kernel - Re: linux-next: build warning after merge of the net-next tree

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Message-ID: <CAK7LNARfZH=ZEdFuRq_g1HsJ+Pv1m=v343JLyE-6+uM_d+3eWA@mail.gmail.com>
Date:   Fri, 20 Jul 2018 08:19:34 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        David Miller <davem@...emloft.net>,
        Networking <netdev@...r.kernel.org>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Lunn <andrew@...n.ch>
Subject: Re: linux-next: build warning after merge of the net-next tree

2018-07-20 7:35 GMT+09:00 Guenter Roeck <linux@...ck-us.net>:
> On Fri, Jul 20, 2018 at 08:09:06AM +1000, Stephen Rothwell wrote:
>> Hi Guenter,
>>
>> On Thu, 19 Jul 2018 06:49:01 -0700 Guenter Roeck <linux@...ck-us.net> wrote:
>> >
>> > On 07/18/2018 10:29 PM, Stephen Rothwell wrote:
>> > >
>> > > On Wed, 18 Jul 2018 20:52:56 -0700 Guenter Roeck <linux@...ck-us.net> wrote:
>> > >>
>> > >> On 07/18/2018 07:04 PM, Stephen Rothwell wrote:
>> > >>>
>> > >>> After merging the net-next tree, today's linux-next build (x86_64
>> > >>> allmodconfig) produced this warning:
>> > >>>
>> > >>> *
>> > >>> * Restart config...
>> > >>> *
>> > >>> ....
>> > >>>
>> > >>> This is output by my "make allmodconfig" and only started after merging
>> > >>> the net-next tree today.  It has continued for further merges/builds.
>> > >>>
>> > >>> I suspect commit
>> > >>>
>> > >>>     1323061a018a ("net: phy: sfp: Add HWMON support for module sensors")
>> > >>>
>> > >>> which added an "imply" clause.
>> > >>>
>> > >> I thought "imply" was better than "depends on HWMON || HWMON=n", but maybe
>> > >> not. Is that a caveat when using "imply", and does it mean that "imply"
>> > >> should better not be used ?
>> > >
>> > > I don't know, sorry.  It was just my best guess from what I could see
>> > > had changed.
>> > >
>> > > I wonder if it makes a difference that I am doing my "make
>> > > allmodconfig" on top of a previous "make allmodconfig" and some symbols
>> > > are marked as "NEW" (though they are not symbols related to the changes
>> > > that happened during the net-next tree merge)?
>> > >
>> >
>> > I tried to reproduce the problem, but I don't see the message.
>> >
>> > What I do see, though, is that "make allmodconfig" on a clean tree,
>> > followed by "make menuconfig", results in configuration changes.
>> > Specifically,
>> >
>> >  > CONFIG_ARC_EMAC_CORE=m
>> >  > CONFIG_ARC_EMAC=m
>> >  > CONFIG_EMAC_ROCKCHIP=m
>> >
>> > is removed by menuconfig, and a large number of "# ... is not set"
>> > configuration lines are added. Weird and bad, since several of the
>> > disabled configurations _should_ be enabled by "make allmodconfig",
>> > and a large number of hwmon drivers are affected. Bisect does point
>> > to "net: phy: sfp: Add HWMON support for module sensors", meaning
>> > "imply hwmon" does have severe side effects and can not be used.
>> >
>> > I'll try to find a fix.
>>
>> OK, my mistake, the "make allmodconfig" works, the following "make"
>> causes the config restart.  (I am actually doing cross builds and using
>> an external object directory, in case that matters.)
>>
>> I removed the "imply HWMON" line added by the above commit and the
>> problem went away.  Also, using "depends on HWMON || HWMON=n" instead
>> of the imply fixes it.
>
> Yes, replacing imply with the dependency is what I did in the fixup patch.
> Sorry, I should have copied you: https://patchwork.kernel.org/patch/10534925/
>
> It is a bit different - imply was supposed to enforce HWMON={y,n} if SFP=y,
> and the depends line enforces SFP={n,m} if HWMON=m. I have no idea why
> imply doesn't work, but I think I'll stay away from it in the future.
>
> Guenter


Hmm, this could be a Kconfig bug.

I will take a look.


BTW,
'depends on HWMON || HWMON=n' is pointless
because it is always true.



-- 
Best Regards
Masahiro Yamada