linux-kernel - Does a simple "make" build the kernel twice ?

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Message-ID: <2f0539e8-ba9d-b49a-0b54-bbe6667d5605@gmx.de>
Date:   Thu, 28 Dec 2017 20:18:09 +0100
From:   Toralf Förster <toralf.foerster@....de>
To:     Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Does a simple "make" build the kernel twice ?

While trying today to bisect a regression between 4.14.8 and 4.14.9 I was wondering about the unusual long build times of each step.

It turns out that a command like this ((make1.log attached):
	sudo make -j1 2>&1 | tee ~/tmp/make1.log
builds everything twice. Does the line 2015:
	UPD     include/generated/autoksyms.h
points to the root cause ? Furthermore it seems that a change of just few files results into a full kernel rebuild (and that twice is explained above). Therefore I stopped bisecting for now. FWIW d120cd749e was one candidate of being a bad commit here at a ThinkPad T440s, but I'm usnsure about that result.

This is a stable hardened Gentoo Linux, GCC is:

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/6.4.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-6.4.0/work/gcc-6.4.0/configure --host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/6.4.0 --includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/6.4.0/include --datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/6.4.0 --mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/6.4.0/man --infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/6.4.0/info --with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/6.4.0/include/g++-v6 --with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/6.4.0/python --enable-languages=c,c++ --enable-obsolete --enable-secureplt --disable-werror --with-system-zlib --enable-nls --without-included-gettext --enable-checking=release --with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo Hardened 6.4.0 p1.1' --enable-esp --enable-libstdcxx-time --disable-libstdcxx-pch --enable-shared --enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu --enable-multilib --with-multilib-list=m32,m64 --disable-altivec --disable-fixed-point --enable-targets=all --disable-libgcj --enable-libgomp --disable-libmudflap --disable-libssp --disable-libcilkrts --disable-libmpx --enable-vtable-verify --enable-libvtv --disable-libquadmath --enable-lto --without-isl --disable-libsanitizer --enable-default-pie --enable-default-ssp
Thread model: posix
gcc version 6.4.0 (Gentoo Hardened 6.4.0 p1.1) 

-- 
Toralf
PGP C4EACDDE 0076E94E

View attachment "make1.log" of type "text/x-log" (177227 bytes)