linux-kernel - Re: [PATCH] kernel.h: Add printk_ratelimited and pr_<level>

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Date:	Mon, 2 Nov 2009 16:58:23 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Joe Perches <joe@...ches.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Naohiro Ooiwa <nooiwa@...aclelinux.com>,
	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>,
	roland@...hat.com, Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>, oleg@...hat.com,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] kernel.h: Add printk_ratelimited and pr_<level>_rl


* Joe Perches <joe@...ches.com> wrote:

> Add a printk_ratelimited statement expression macro that uses a 
> per-call ratelimit_state so that multiple subsystems output messages 
> are not suppressed by a global __ratelimit state.
> 
> Signed-off-by: Joe Perches <joe@...ches.com>
> 
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index f4e3184..555560c 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -407,6 +407,50 @@ static inline char *pack_hex_byte(char *buf, u8 byte)
>  #endif
>  
>  /*
> + * ratelimited messages with local ratelimit_state,
> + * no local ratelimit_state used in the !PRINTK case
> + */
> +#ifdef CONFIG_PRINTK
> +#define printk_ratelimited(fmt, ...)  ({		\
> +	static struct ratelimit_state _rs = {		\
> +		.interval = DEFAULT_RATELIMIT_INTERVAL, \
> +		.burst = DEFAULT_RATELIMIT_BURST,       \
> +	};                                              \
> +							\
> +	if (!__ratelimit(&_rs))                         \
> +		printk(fmt, ##__VA_ARGS__);		\
> +})
> +#else
> +/* No effect, but we still get type checking even in the !PRINTK case: */
> +#define printk_ratelimited printk
> +#endif
> +
> +#define pr_emerg_rl(fmt, ...) \
> +        printk_ratelimited(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__)
> +#define pr_alert_rl(fmt, ...) \
> +        printk_ratelimited(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__)
> +#define pr_crit_rl(fmt, ...) \
> +        printk_ratelimited(KERN_CRIT pr_fmt(fmt), ##__VA_ARGS__)
> +#define pr_err_rl(fmt, ...) \
> +        printk_ratelimited(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__)
> +#define pr_warning_rl(fmt, ...) \
> +        printk_ratelimited(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
> +#define pr_notice_rl(fmt, ...) \
> +        printk_ratelimited(KERN_NOTICE pr_fmt(fmt), ##__VA_ARGS__)
> +#define pr_info_rl(fmt, ...) \
> +        printk_ratelimited(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
> +/* no pr_cont_rl, don't do that... */
> +/* If you are writing a driver, please use dev_dbg instead */
> +#if defined(DEBUG)
> +#define pr_debug_rl(fmt, ...) \
> +	printk_ratelimited(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
> +#else
> +#define pr_debug_rl(fmt, ...) \
> +	({ if (0) printk_ratelimited(KERN_DEBUG pr_fmt(fmt), \
> +				     ##__VA_ARGS__); 0; })
> +#endif
> +

Looks like a useful addition. Somewhat bloatier, but then again, more 
correct and the bloat problem can be solved by explicit state 
definitions.

	Ingo
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