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[176.157.204.145]) by smtp.gmail.com with ESMTPSA id y3-20020adfee03000000b003368c8d120fsm18286005wrn.7.2024.01.24.00.56.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Jan 2024 00:56:52 -0800 (PST) Message-ID: Date: Wed, 24 Jan 2024 09:56:52 +0100 Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] kconfig: remove unneeded symbol_empty variable Content-Language: en-US To: Masahiro Yamada Cc: Geert Uytterhoeven , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, Linux-Renesas , Vegard Nossum References: <20231125163559.824210-1-masahiroy@kernel.org> From: Yoann Congal Organization: Smile ECS In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Le 24/01/2024 à 09:09, Masahiro Yamada a écrit : > On Wed, Jan 24, 2024 at 12:11 AM Yoann Congal wrote: >> >> Le 23/01/2024 à 13:54, Geert Uytterhoeven a écrit : >>> Hi Yamada-san, >> >> Hello, >> >>> On Sat, Nov 25, 2023 at 5:36 PM Masahiro Yamada wrote: >>>> This is used only for initializing other variables. >>>> >>>> Use the empty string "". >>>> >>>> Please note newval.tri is unused for S_INT/HEX/STRING. >>>> >>>> Signed-off-by: Masahiro Yamada >>> >>> Thanks for your patch, which is now commit 4e244c10eab345a7 >>> ("kconfig: remove unneeded symbol_empty variable") in v6.8-rc1. >>> >>> When running "make _defconfig" with _defconfig an SMP >>> defconfig without explicit configuration of CONFIG_LOG_CPU_MAX_BUF_SHIFT, >>> the aforementioned commit causes a change in the generated .config: >>> >>> -CONFIG_LOG_CPU_MAX_BUF_SHIFT=12 >>> +CONFIG_LOG_CPU_MAX_BUF_SHIFT=0 >>> >>> It looks like CONFIG_BASE_SMALL=0 is treated as a string instead of >>> the integer number zero? >>> >>> init/Kconfig=config LOG_CPU_MAX_BUF_SHIFT >>> init/Kconfig- int "CPU kernel log buffer size contribution (13 => 8 >>> KB, 17 => 128KB)" >>> init/Kconfig- depends on SMP >>> init/Kconfig- range 0 21 >>> init/Kconfig: default 12 if !BASE_SMALL >>> init/Kconfig: default 0 if BASE_SMALL >>> >>> Note that reverting 4e244c10eab345a7 is not sufficient to fix the issue. >>> Also reverting commit 6262afa10ef7cc8f ("kconfig: default to zero if >>> int/hex symbol lacks default property") does fix it. >> >> (Since I'd really like 6262afa10ef7cc8f ("kconfig: default to zero if int/hex symbol lacks default property") to stay, allow me to try to help) >> >> The problem is quite easy to reproduce: >> $ make x86_64_defconfig >> $ grep 'LOG_CPU_MAX_BUF_SHIFT\|BASE_SMALL\|BASE_FULL' .config >> CONFIG_LOG_CPU_MAX_BUF_SHIFT=0 >> CONFIG_BASE_FULL=y >> CONFIG_BASE_SMALL=0 >> Here, CONFIG_LOG_CPU_MAX_BUF_SHIFT should be 12 not 0. > > > > I could not produce it in this way. > I ran the same commands as yours. > > CONFIG_LOG_CPU_MAX_BUF_SHIFT=12 for me. > > > > masahiro@zoe:~/ref/linux(master)$ git describe > v6.8-rc1-29-g615d30064886 > masahiro@zoe:~/ref/linux(master)$ git diff > masahiro@zoe:~/ref/linux(master)$ make x86_64_defconfig > # > # No change to .config > # You already had a .config with the correct value of LOG_CPU_MAX_BUF_SHIFT (Maybe?) > masahiro@zoe:~/ref/linux(master)$ grep > 'LOG_CPU_MAX_BUF_SHIFT\|BASE_SMALL\|BASE_FULL' .config > CONFIG_LOG_CPU_MAX_BUF_SHIFT=12 > CONFIG_BASE_FULL=y > CONFIG_BASE_SMALL=0 Try to remove the existing .config: $ git describe v6.8-rc1 $ git diff $ rm .config -f $ make x86_64_defconfig # # configuration written to .config # $ grep 'LOG_CPU_MAX_BUF_SHIFT\|BASE_SMALL\|BASE_FULL' .config CONFIG_LOG_CPU_MAX_BUF_SHIFT=0 CONFIG_BASE_FULL=y CONFIG_BASE_SMALL=0 >> >> For what it is worth, CONFIG_BASE_SMALL is defined as an int but is only used as a bool : >> $ git grep BASE_SMALL >> arch/x86/include/asm/mpspec.h:#if CONFIG_BASE_SMALL == 0 >> drivers/tty/vt/vc_screen.c:#define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE) >> include/linux/threads.h:#define PID_MAX_DEFAULT (CONFIG_BASE_SMALL ? 0x1000 : 0x8000) >> include/linux/threads.h:#define PID_MAX_LIMIT (CONFIG_BASE_SMALL ? PAGE_SIZE * 8 : \ >> include/linux/udp.h:#define UDP_HTABLE_SIZE_MIN (CONFIG_BASE_SMALL ? 128 : 256) >> include/linux/xarray.h:#define XA_CHUNK_SHIFT (CONFIG_BASE_SMALL ? 4 : 6) >> init/Kconfig: default 12 if !BASE_SMALL >> init/Kconfig: default 0 if BASE_SMALL >> init/Kconfig:config BASE_SMALL >> kernel/futex/core.c:#if CONFIG_BASE_SMALL >> kernel/user.c:#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7) >> >> Maybe we should change CONFIG_BASE_SMALL to the bool type? My first test shows that switching CONFIG_BASE_SMALL to bool type does fix the LOG_CPU_MAX_BUF_SHIFT default value. >> I'll poke around to see if I can understand why a int="0" is true for kconfig. Here's what I understood: To get the default value of LOG_CPU_MAX_BUF_SHIFT, kconfig calls sym_get_default_prop(LOG_CPU_MAX_BUF_SHIFT) -> expr_calc_value("BASE_SMALL" as an expr) -> sym_calc_value(BASE_SMALL as a symbol) and returns sym->curr.tri But, if I understood correctly, sym_calc_value() does not set sym->curr.tri in case of a int type config. Regards, -- Yoann Congal Smile ECS - Tech Expert