linux-kernel - Re: [PATCH v2 1/3] printk: introduce new macros pr_<level>

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Date:   Fri, 25 Nov 2022 12:18:39 -0800
From:   Joe Perches <joe@...ches.com>
To:     Thomas Weißschuh <linux@...ssschuh.net>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        linux-pm@...r.kernel.org, Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andy Whitcroft <apw@...onical.com>
Cc:     linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        Dwaipayan Ray <dwaipayanray1@...il.com>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>
Subject: Re: [PATCH v2 1/3] printk: introduce new macros pr_<level>_cont()

On Fri, 2022-11-25 at 20:09 +0100, Thomas Weißschuh wrote:
> These macros emit continuation messages with explicit levels.
> In case the continuation is logged separately from the original message
> it will retain its level instead of falling back to KERN_DEFAULT.
> 
> This remedies the issue that logs filtered by level contain stray
> continuation messages without context.
> 
> Suggested-by: Petr Mladek <pmladek@...e.com>
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> ---
>  include/linux/printk.h | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/include/linux/printk.h b/include/linux/printk.h
> index 8c81806c2e99..8f564c38f121 100644
> --- a/include/linux/printk.h
> +++ b/include/linux/printk.h
> @@ -537,6 +537,8 @@ struct pi_entry {
>   * This macro expands to a printk with KERN_CONT loglevel. It should only be
>   * used when continuing a log message with no newline ('\n') enclosed. Otherwise
>   * it defaults back to KERN_DEFAULT loglevel.
> + *
> + * Use the dedicated pr_<level>_cont() macros instead.
>   */
>  #define pr_cont(fmt, ...) \
>  	printk(KERN_CONT fmt, ##__VA_ARGS__)
> @@ -701,6 +703,27 @@ do {									\
>  	no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
>  #endif
>  
> +/*
> + * Print a continuation message with level. In case the continuation is split
> + * from the main message it preserves the level.
> + */
> +
> +#define pr_emerg_cont(fmt, ...)					\
> +	printk(KERN_EMERG KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)

Aren't this rather backwards?
KERN_CONT KERN_<LEVEL> seems to make more sense to me.

> +#define pr_alert_cont(fmt, ...)					\
> +	printk(KERN_ALERT KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
> +#define pr_crit_cont(fmt, ...)					\
> +	printk(KERN_CRIT KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
> +#define pr_err_cont(fmt, ...)					\
> +	printk(KERN_ERR KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
> +#define pr_warn_cont(fmt, ...)					\
> +	printk(KERN_WARN KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
> +#define pr_notice_cont(fmt, ...)					\
> +	printk(KERN_NOTICE KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
> +#define pr_info_cont(fmt, ...)					\
> +	printk(KERN_INFO KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
> +/* no pr_debug_ratelimited, it doesn't make sense with CONFIG_DYNAMIC_DEBUG. */
> +
>  extern const struct file_operations kmsg_fops;
>  
>  enum {