linux-kernel - Re: [RFC/PATCH] ratelimit: make output more useful

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Date:	Fri, 23 Oct 2009 13:33:48 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Christian Borntraeger <borntraeger@...ibm.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Young <hidave.darkstar@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC/PATCH] ratelimit: make output more useful


* Christian Borntraeger <borntraeger@...ibm.com> wrote:

> Today I got 
> 
> 
> [39648.224782] Registered led device: iwl-phy0::TX
> [40676.545099] __ratelimit: 246 callbacks suppressed
> [40676.545103] abcdef[23675]: segfault at 0 ...
> 
> as you can see the ratelimit message contains a function prefix. Since this is 
> always __ratelimit, this wont help much. This patch changes __ratelimit and 
> printk_ratelimit to print the function name  that calls ratelimit.
> 
> Opinions?
> 
> Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
> 
> CC: Andrew Morton <akpm@...ux-foundation.org>
> CC: Ingo Molnar <mingo@...e.hu>
> CC: Dave Young <hidave.darkstar@...il.com>
> 
>  include/linux/kernel.h    |    6 +++++-
>  include/linux/ratelimit.h |    3 ++-
>  kernel/printk.c           |    9 +--------
>  lib/ratelimit.c           |    6 +++---
>  4 files changed, 11 insertions(+), 13 deletions(-)
> 
> Index: linux-2.6/include/linux/kernel.h
> ===================================================================
> --- linux-2.6.orig/include/linux/kernel.h
> +++ linux-2.6/include/linux/kernel.h
> @@ -241,8 +241,12 @@ asmlinkage int vprintk(const char *fmt, 
>  asmlinkage int printk(const char * fmt, ...)
>  	__attribute__ ((format (printf, 1, 2))) __cold;
>  
> +/*
> + * printk rate limiting, lifted from the networking subsystem.
> + */
>  extern struct ratelimit_state printk_ratelimit_state;
> -extern int printk_ratelimit(void);
> +#define printk_ratelimit() ___ratelimit(&printk_ratelimit_state, __func__)
> +
>  extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
>  				   unsigned int interval_msec);
>  
> Index: linux-2.6/include/linux/ratelimit.h
> ===================================================================
> --- linux-2.6.orig/include/linux/ratelimit.h
> +++ linux-2.6/include/linux/ratelimit.h
> @@ -16,5 +16,6 @@ struct ratelimit_state {
>  #define DEFINE_RATELIMIT_STATE(name, interval, burst)		\
>  		struct ratelimit_state name = {interval, burst,}
>  
> -extern int __ratelimit(struct ratelimit_state *rs);
> +extern int ___ratelimit(struct ratelimit_state *rs, const char *func);
> +#define __ratelimit(state) ___ratelimit(state, __func__)
>  #endif
> Index: linux-2.6/kernel/printk.c
> ===================================================================
> --- linux-2.6.orig/kernel/printk.c
> +++ linux-2.6/kernel/printk.c
> @@ -1369,18 +1369,11 @@ late_initcall(disable_boot_consoles);
>  #if defined CONFIG_PRINTK
>  
>  /*
> - * printk rate limiting, lifted from the networking subsystem.
> - *
>   * This enforces a rate limit: not more than 10 kernel messages
>   * every 5s to make a denial-of-service attack impossible.
>   */
>  DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
> -
> -int printk_ratelimit(void)
> -{
> -	return __ratelimit(&printk_ratelimit_state);
> -}
> -EXPORT_SYMBOL(printk_ratelimit);
> +EXPORT_SYMBOL(printk_ratelimit_state);
>  
>  /**
>   * printk_timed_ratelimit - caller-controlled printk ratelimiting
> Index: linux-2.6/lib/ratelimit.c
> ===================================================================
> --- linux-2.6.orig/lib/ratelimit.c
> +++ linux-2.6/lib/ratelimit.c
> @@ -23,7 +23,7 @@ static DEFINE_SPINLOCK(ratelimit_lock);
>   * This enforces a rate limit: not more than @rs->ratelimit_burst callbacks
>   * in every @rs->ratelimit_jiffies
>   */
> -int __ratelimit(struct ratelimit_state *rs)
> +int ___ratelimit(struct ratelimit_state *rs, const char *func)
>  {
>  	unsigned long flags;
>  
> @@ -37,7 +37,7 @@ int __ratelimit(struct ratelimit_state *
>  	if (time_is_before_jiffies(rs->begin + rs->interval)) {
>  		if (rs->missed)
>  			printk(KERN_WARNING "%s: %d callbacks suppressed\n",
> -				__func__, rs->missed);
> +				func, rs->missed);
>  		rs->begin = 0;
>  		rs->printed = 0;
>  		rs->missed = 0;
> @@ -54,4 +54,4 @@ print:
>  	spin_unlock_irqrestore(&ratelimit_lock, flags);
>  	return 1;
>  }
> -EXPORT_SYMBOL(__ratelimit);
> +EXPORT_SYMBOL(___ratelimit);

Makes quite a bit of sense.

Mind sending it against latest tip:master (or tip:core/printk):

  http://people.redhat.com/mingo/tip.git/README

Which has a couple of ratelimit changes queued up already that collide 
with your patch:

Hunk #1 FAILED at 241.
1 out of 1 hunk FAILED -- rejects in file include/linux/kernel.h
patching file include/linux/ratelimit.h
Hunk #1 FAILED at 16.
1 out of 1 hunk FAILED -- rejects in file include/linux/ratelimit.h
patching file kernel/printk.c
Hunk #1 succeeded at 1357 (offset -12 lines).
patching file lib/ratelimit.c
Hunk #1 succeeded at 20 with fuzz 1 (offset -3 lines).
Hunk #2 FAILED at 34.
Hunk #3 succeeded at 62 with fuzz 2 (offset 8 lines).
1 out of 3 hunks FAILED -- rejects in file lib/ratelimit.c

Thanks,

	Ingo
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