linux-kernel - Re: [dborkman:pr/bpf-cgrp 2/4] include/linux/cgroup-defs.h:771:70: warning: unused parameter 'skcd'

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Date:   Mon, 13 Sep 2021 11:00:10 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     kernel test robot <lkp@...el.com>, llvm@...ts.linux.dev,
        kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
        philip.li@...el.com, alexei.starovoitov@...il.com,
        andrii@...nel.org
Subject: Re: [dborkman:pr/bpf-cgrp 2/4] include/linux/cgroup-defs.h:771:70:
 warning: unused parameter 'skcd'

Hi Daniel,

On Mon, Sep 13, 2021 at 05:19:26PM +0200, Daniel Borkmann wrote:
> [ +Philip ]
> 
> On 9/11/21 2:38 AM, kernel test robot wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/dborkman/bpf.git pr/bpf-cgrp
> > head:   5a6e78baee7515884b93a90c5d03db601bc9063a
> > commit: f36377d0c40cce0cdeaff50031c268bc640d94f0 [2/4] bpf, cgroups: Fix cgroup v2 fallback on v1/v2 mixed mode
> > config: i386-randconfig-r032-20210910 (attached as .config)
> > compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 261cbe98c38f8c1ee1a482fe76511110e790f58a)
> > reproduce (this is a W=1 build):
> >          wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> >          chmod +x ~/bin/make.cross
> >          # https://git.kernel.org/pub/scm/linux/kernel/git/dborkman/bpf.git/commit/?id=f36377d0c40cce0cdeaff50031c268bc640d94f0
> >          git remote add dborkman https://git.kernel.org/pub/scm/linux/kernel/git/dborkman/bpf.git
> >          git fetch --no-tags dborkman pr/bpf-cgrp
> >          git checkout f36377d0c40cce0cdeaff50031c268bc640d94f0
> >          # save the attached .config to linux build tree
> >          COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=i386
> > 
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@...el.com>
> > 
> > All warnings (new ones prefixed by >>):
> 
> Not sure how useful these warnings below are given it is quite conventional in the kernel
> to have some static inline helper which e.g. look:
> 
> static inline int bla(struct foo *bar)
> {
> #ifdef CONFIG_<XYZ>
>         return ... /// do something with bar
> #else
>         return 0;
> #endif
> }
> 
> I presume consensus here is to ignore these given also the gazillion other cases in the
> kernel tree. In other words, goal on -Wunused-parameter for kernel would be to really
> only catch cases where a parameter is indeed in all cases unused and should be removed
> from the signature.

Unfortunately, it looks like you are getting bit by a tangential issue
here:

https://lore.kernel.org/r/YSQE2f5teuvKLkON@Ryzen-9-3900X.localdomain/

The full include log:

In file included from drivers/gpu/drm/i915/display/intel_dpll.c:7:
In file included from drivers/gpu/drm/i915/display/intel_de.h:9:
In file included from ./drivers/gpu/drm/i915/i915_drv.h:39:
In file included from ./include/linux/i2c.h:18:
In file included from ./include/linux/regulator/consumer.h:35:
In file included from ./include/linux/suspend.h:5:
In file included from ./include/linux/swap.h:9:
In file included from ./include/linux/memcontrol.h:13:
In file included from ./include/linux/cgroup.h:28:
In file included from ./include/linux/cgroup-defs.h:22:
In file included from ./include/linux/bpf-cgroup.h:5:
./include/linux/bpf.h:770:61: warning: unused parameter 'prog' [-Wunused-parameter]
static inline int bpf_trampoline_link_prog(struct bpf_prog *prog,
                                                            ^
./include/linux/bpf.h:771:32: warning: unused parameter 'tr' [-Wunused-parameter]
                                           struct bpf_trampoline *tr)
                                                                  ^
...

The fixes are here:

https://lore.kernel.org/r/20210824022640.2170859-1-nathan@kernel.org/
https://lore.kernel.org/r/20210824232237.2085342-1-nathan@kernel.org/

I will push to get these fixes accepted as quickly as possible.

Philip, would it be possible for you guys to avoid sending reports for
i386 configurations that contain any of the following three
configurations for the time being?

CONFIG_MCRUSOE=y
CONFIG_MEFFICEON=y
CONFIG_MCYRIXIII=y

They are resulting in a lot of false positives, as I have linked above.

Cheers,
Nathan