linux-kernel - Re: Odd build breakage in 4.9-rc7

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Date:   Wed, 30 Nov 2016 21:52:30 +0100
From:   Paul Bolle <pebolle@...cali.nl>
To:     Jarod Wilson <jarod@...hat.com>
Cc:     Tony Luck <tony.luck@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Prarit Bhargava <prarit@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: Odd build breakage in 4.9-rc7

On Wed, 2016-11-30 at 12:24 -0500, Jarod Wilson wrote:
> Up second, once we're past the above, building modules goes splat:
> 
> ----8<----
> $ make -s ARCH=x86_64 V=1 -j8 modules
> ...
> ERROR: "module_put" [virt/lib/irqbypass.ko] undefined!
> ERROR: "mutex_unlock" [virt/lib/irqbypass.ko] undefined!
> ERROR: "mutex_lock" [virt/lib/irqbypass.ko] undefined!
> ...
> ----8<----
> 
> There are similar ERROR lines to the tune of 145k lines of output,
> basically for every single module and symbol in the build. This breakage
> was bisected to commit cd3caefb4663e3811d37cc2afad3cce642d60061, which
> looks fairly innocuous, but when reverted, builds work fine again.

I ran into a modules build printing over 100K ERROR lines a month ago:
    https://lkml.kernel.org/r/<1478165881-9263-1-git-send-email-pebolle@...cali.nl>

That had to do with setting TRIM_UNUSED_KSYMS and so unsetting UNUSED_SYMBOLS,
as far as I could tell. Did you perhaps also have UNUSED_SYMBOLS unset when
your modules build when splat?

And did your bzImage build by any chance print this (to stderr):
    sed: can't read .tmp_versions/*.mod: No such file or directory

If so I might have run into your second issue a month ago already, which makes
your bisect to commit cd3caefb4663 ("Fix subtle CONFIG_MODVERSIONS problems")
suspect. Or did that bisect not cover the second issue?

> Multi-threaded make vs. single-threaded doesn't matter, setting
> CONFIG_BROKEN=y or '# CONFIG_MODVERSIONS is not set' don't make a
> difference, and interestingly, if instead of split 'make bzImage' and
> 'make modules', I just do a single 'make', then things DO build
> successfully, so I'm a wee bit baffled as to what's actually going on
> here.

Likewise (ie, both the modules splat going away if doing a single make and
being baffled, but more that a wee bit).


Paul Bolle