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

On Fri, Jul 20, 2018 at 08:19:34AM +0900, Masahiro Yamada wrote:

2018-07-20 7:35 GMT+09:00 Guenter Roeck [off-list ref]:

quoted

On Fri, Jul 20, 2018 at 08:09:06AM +1000, Stephen Rothwell wrote:

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Hi Guenter,

On Thu, 19 Jul 2018 06:49:01 -0700 Guenter Roeck [off-list ref] wrote:

quoted

On 07/18/2018 10:29 PM, Stephen Rothwell wrote:

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On Wed, 18 Jul 2018 20:52:56 -0700 Guenter Roeck [off-list ref] wrote:

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On 07/18/2018 07:04 PM, Stephen Rothwell wrote:

quoted

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.

I disagree. Its purpose is to enforce SFP=m if HWMON=m while still
permitting HWMON=n.

Guenter