linux-kernel - Re: [PATCH] Remove orphaned CONFIG_PRINTK_SAFE_LOG_BUF

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Message-ID: <87r0ujs9id.fsf@jogness.linutronix.de>
Date:   Tue, 21 Feb 2023 09:39:30 +0106
From:   John Ogness <john.ogness@...utronix.de>
To:     Marc Aurèle La France <tsi@...oix.net>,
        linux-kernel@...r.kernel.org
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] Remove orphaned CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT

(Added the rest of the printk team CC.)

On 2023-02-20, Marc Aurèle La France <tsi@...oix.net> wrote:
> After 93d102f094be9beab28e5afb656c188b16a3793b "printk: remove safe buffers",
> CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT is no longer useful.  Remove it.
>
> This change is not eligible for stable@.
>
> Please Reply-To-All.
>
> Marc.
>
> Signed-off-by: Marc Aurèle La France <tsi@...oix.net>

Reviewed-by: John Ogness <john.ogness@...utronix.de>

> diff -aNpRruz -X /etc/diff.excludes linux-6.2.0/arch/powerpc/configs/microwatt_defconfig devel-6.2.0/arch/powerpc/configs/microwatt_defconfig
> --- linux-6.2.0/arch/powerpc/configs/microwatt_defconfig	2023-02-19 15:24:22.000000000 -0700
> +++ devel-6.2.0/arch/powerpc/configs/microwatt_defconfig	2023-02-20 21:39:39.057268798 -0700
> @@ -4,7 +4,6 @@ CONFIG_HIGH_RES_TIMERS=y
>  CONFIG_PREEMPT_VOLUNTARY=y
>  CONFIG_TICK_CPU_ACCOUNTING=y
>  CONFIG_LOG_BUF_SHIFT=16
> -CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT=12
>  CONFIG_CGROUPS=y
>  CONFIG_BLK_DEV_INITRD=y
>  CONFIG_CC_OPTIMIZE_FOR_SIZE=y
> diff -aNpRruz -X /etc/diff.excludes linux-6.2.0/arch/riscv/configs/nommu_k210_defconfig devel-6.2.0/arch/riscv/configs/nommu_k210_defconfig
> --- linux-6.2.0/arch/riscv/configs/nommu_k210_defconfig	2023-02-19 15:24:22.000000000 -0700
> +++ devel-6.2.0/arch/riscv/configs/nommu_k210_defconfig	2023-02-20 21:40:01.349181760 -0700
> @@ -1,6 +1,5 @@
>  # CONFIG_CPU_ISOLATION is not set
>  CONFIG_LOG_BUF_SHIFT=13
> -CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT=12
>  CONFIG_BLK_DEV_INITRD=y
>  # CONFIG_RD_GZIP is not set
>  # CONFIG_RD_BZIP2 is not set
> diff -aNpRruz -X /etc/diff.excludes linux-6.2.0/arch/riscv/configs/nommu_k210_sdcard_defconfig devel-6.2.0/arch/riscv/configs/nommu_k210_sdcard_defconfig
> --- linux-6.2.0/arch/riscv/configs/nommu_k210_sdcard_defconfig	2023-02-19 15:24:22.000000000 -0700
> +++ devel-6.2.0/arch/riscv/configs/nommu_k210_sdcard_defconfig	2023-02-20 21:39:46.721238871 -0700
> @@ -1,6 +1,5 @@
>  # CONFIG_CPU_ISOLATION is not set
>  CONFIG_LOG_BUF_SHIFT=13
> -CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT=12
>  CONFIG_CC_OPTIMIZE_FOR_SIZE=y
>  # CONFIG_SYSFS_SYSCALL is not set
>  # CONFIG_FHANDLE is not set
> diff -aNpRruz -X /etc/diff.excludes linux-6.2.0/arch/riscv/configs/nommu_virt_defconfig devel-6.2.0/arch/riscv/configs/nommu_virt_defconfig
> --- linux-6.2.0/arch/riscv/configs/nommu_virt_defconfig	2023-02-19 15:24:22.000000000 -0700
> +++ devel-6.2.0/arch/riscv/configs/nommu_virt_defconfig	2023-02-20 21:39:55.329205262 -0700
> @@ -1,6 +1,5 @@
>  # CONFIG_CPU_ISOLATION is not set
>  CONFIG_LOG_BUF_SHIFT=16
> -CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT=12
>  CONFIG_BLK_DEV_INITRD=y
>  # CONFIG_RD_BZIP2 is not set
>  # CONFIG_RD_LZMA is not set
> diff -aNpRruz -X /etc/diff.excludes linux-6.2.0/init/Kconfig devel-6.2.0/init/Kconfig
> --- linux-6.2.0/init/Kconfig	2023-02-19 15:24:22.000000000 -0700
> +++ devel-6.2.0/init/Kconfig	2023-02-20 21:40:23.329095967 -0700
> @@ -769,30 +769,6 @@ config LOG_CPU_MAX_BUF_SHIFT
>  		     13 =>   8 KB for each CPU
>  		     12 =>   4 KB for each CPU
>
> -config PRINTK_SAFE_LOG_BUF_SHIFT
> -	int "Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)"
> -	range 10 21
> -	default 13
> -	depends on PRINTK
> -	help
> -	  Select the size of an alternate printk per-CPU buffer where messages
> -	  printed from unsafe contexts are temporary stored. One example would
> -	  be NMI messages, another one - printk recursion. The messages are
> -	  copied to the main log buffer in a safe context to avoid a deadlock.
> -	  The value defines the size as a power of 2.
> -
> -	  Those messages are rare and limited. The largest one is when
> -	  a backtrace is printed. It usually fits into 4KB. Select
> -	  8KB if you want to be on the safe side.
> -
> -	  Examples:
> -		     17 => 128 KB for each CPU
> -		     16 =>  64 KB for each CPU
> -		     15 =>  32 KB for each CPU
> -		     14 =>  16 KB for each CPU
> -		     13 =>   8 KB for each CPU
> -		     12 =>   4 KB for each CPU
> -
>  config PRINTK_INDEX
>  	bool "Printk indexing debugfs interface"
>  	depends on PRINTK && DEBUG_FS

Thanks!

John Ogness