linux-kernel - RE: [PATCH v2] x86/resctrl: Fix unused variable warning in cache_alloc_hsw

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Message-ID: <SJ1PR11MB6083E6ABE4D467D5D275A309FCA6A@SJ1PR11MB6083.namprd11.prod.outlook.com>
Date:   Thu, 2 Nov 2023 22:50:00 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     "Chatre, Reinette" <reinette.chatre@...el.com>,
        "Moger, Babu" <babu.moger@....com>
CC:     "Yu, Fenghua" <fenghua.yu@...el.com>,
        Peter Newman <peternewman@...gle.com>,
        "x86@...nel.org" <x86@...nel.org>,
        Shaopeng Tan <tan.shaopeng@...itsu.com>,
        James Morse <james.morse@....com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: RE: [PATCH v2] x86/resctrl: Fix unused variable warning in
 cache_alloc_hsw_probe()

> This does seem a valid issue and my Ack remains. I'm just puzzled why I do not
> encounter the same warning.

Reinette,

Some other CONFIG option changing CFLAGS?

Here's what I have for a "make V=1 W=1" for core.o

# CC      arch/x86/kernel/cpu/resctrl/core.o
  gcc -Wp,-MMD,arch/x86/kernel/cpu/resctrl/.core.o.d -nostdinc -I./arch/x86/include -I./arch/x86/include/generated  -I./include -I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/compiler-version.h -include ./include/linux/kconfig.h -include ./include/linux/compiler_types.h -D__KERNEL__ -fmacro-prefix-map=./= -Wundef -DKBUILD_EXTRA_WARN1 -std=gnu11 -fshort-wchar -funsigned-char -fno-common -fno-PIE -fno-strict-aliasing -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -fcf-protection=none -m64 -falign-jumps=1 -falign-loops=1 -mno-80387 -mno-fp-ret-in-387 -mpreferred-stack-boundary=3 -mskip-rax-setup -mtune=generic -mno-red-zone -mcmodel=kernel -Wno-sign-compare -fno-asynchronous-unwind-tables -mindirect-branch=thunk-extern -mindirect-branch-register -mindirect-branch-cs-prefix -mfunction-return=thunk-extern -fno-jump-tables -mharden-sls=all -fpatchable-function-entry=16,16 -fno-delete-null-pointer-checks -O2 -fno-allow-store-data-races -fstack-protector-strong -ftrivial-auto-var-init=zero -fno-stack-clash-protection -pg -mrecord-mcount -mfentry -DCC_USING_FENTRY -falign-functions=16 -fstrict-flex-arrays=3 -fno-strict-overflow -fno-stack-check -fconserve-stack -Wall -Wundef -Werror=implicit-function-declaration -Werror=implicit-int -Werror=return-type -Werror=strict-prototypes -Wno-format-security -Wno-trigraphs -Wno-frame-address -Wno-address-of-packed-member -Wframe-larger-than=2048 -Wno-main -Wno-unused-but-set-variable -Wno-unused-const-variable -Wno-dangling-pointer -Wvla -Wno-pointer-sign -Wcast-function-type -Wno-array-bounds -Wno-alloc-size-larger-than -Wimplicit-fallthrough=5 -Werror=date-time -Werror=incompatible-pointer-types -Werror=designated-init -Wenum-conversion -Wextra -Wunused -Wno-unused-parameter -Wmissing-declarations -Wrestrict -Wmissing-format-attribute -Wmissing-prototypes -Wold-style-definition -Wmissing-include-dirs -Wunused-but-set-variable -Wunused-const-variable -Wpacked-not-aligned -Wformat-overflow -Wformat-truncation -Wstringop-overflow -Wstringop-truncation -Wno-missing-field-initializers -Wno-type-limits -Wno-shift-negative-value -Wno-maybe-uninitialized -Wno-sign-compare -g    -DKBUILD_MODFILE='"arch/x86/kernel/cpu/resctrl/core"' -DKBUILD_BASENAME='"core"' -DKBUILD_MODNAME='"core"' -D__KBUILD_MODNAME=kmod_core -c -o arch/x86/kernel/cpu/resctrl/core.o arch/x86/kernel/cpu/resctrl/core.c   ; ./tools/objtool/objtool --hacks=jump_label --hacks=noinstr --hacks=skylake --orc --retpoline --rethunk --sls --static-call --uaccess --prefix=16   arch/x86/kernel/cpu/resctrl/core.o
arch/x86/kernel/cpu/resctrl/core.c: In function ‘cache_alloc_hsw_probe’:
arch/x86/kernel/cpu/resctrl/core.c:139:16: warning: variable ‘h’ set but not used [-Wunused-but-set-variable]
  139 |         u32 l, h, max_cbm = BIT_MASK(20) - 1;
      |                ^

Dropping just the "-Wunused-but-set-variable" from that big mess does make the warning disappear for me.

But maybe some option can result in the argument list being built in a different order? I see there is an earlier " -Wno-unused-but-set-variable"

-Tony