linux-kernel - Re: [PATCH -v3 1/2] ratelimit: Extend to print suppressed messages on release

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Date:	Tue, 5 Jul 2016 14:26:48 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Franck Bui <fbui@...e.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH -v3 1/2] ratelimit: Extend to print suppressed messages
 on release

On Mon,  4 Jul 2016 16:24:51 +0200
Borislav Petkov <bp@...en8.de> wrote:

> From: Borislav Petkov <bp@...e.de>
> 
> Extend the ratelimiting facility to print the amount of suppressed lines
> when it is being released.
> 
> Separated from a previous patch by Linus.
> 
> Also, make the ON_RELEASE image not use "callbacks" as it is misleading.
> 
> Signed-off-by: Borislav Petkov <bp@...e.de>
> Acked-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Franck Bui <fbui@...e.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> ---
>  include/linux/ratelimit.h | 36 +++++++++++++++++++++++++++++++-----
>  lib/ratelimit.c           |  6 ++++--
>  2 files changed, 35 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/ratelimit.h b/include/linux/ratelimit.h
> index 18102529254e..1d8a17ee8395 100644
> --- a/include/linux/ratelimit.h
> +++ b/include/linux/ratelimit.h
> @@ -2,11 +2,15 @@
>  #define _LINUX_RATELIMIT_H
>  
>  #include <linux/param.h>
> +#include <linux/sched.h>
>  #include <linux/spinlock.h>
>  
>  #define DEFAULT_RATELIMIT_INTERVAL	(5 * HZ)
>  #define DEFAULT_RATELIMIT_BURST		10
>  
> +/* issue num suppressed message on exit */
> +#define RATELIMIT_MSG_ON_RELEASE	BIT(0)
> +
>  struct ratelimit_state {
>  	raw_spinlock_t	lock;		/* protect the state */
>  
> @@ -15,6 +19,7 @@ struct ratelimit_state {
>  	int		printed;
>  	int		missed;
>  	unsigned long	begin;
> +	unsigned long	flags;
>  };
>  
>  #define RATELIMIT_STATE_INIT(name, interval_init, burst_init) {		\
> @@ -34,12 +39,33 @@ struct ratelimit_state {
>  static inline void ratelimit_state_init(struct ratelimit_state *rs,
>  					int interval, int burst)
>  {
> +	memset(rs, 0, sizeof(*rs));
> +
>  	raw_spin_lock_init(&rs->lock);
> -	rs->interval = interval;
> -	rs->burst = burst;
> -	rs->printed = 0;
> -	rs->missed = 0;
> -	rs->begin = 0;
> +	rs->interval	= interval;
> +	rs->burst	= burst;
> +}
> +
> +static inline void ratelimit_default_init(struct ratelimit_state *rs)
> +{
> +	return ratelimit_state_init(rs, DEFAULT_RATELIMIT_INTERVAL,
> +					DEFAULT_RATELIMIT_BURST);
> +}
> +
> +static inline void ratelimit_state_exit(struct ratelimit_state *rs)
> +{
> +	if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE))
> +		return;
> +
> +	if (rs->missed)
> +		printk(KERN_WARNING "%s: %d output lines suppressed due to ratelimiting\n",
> +		       current->comm, rs->missed);

Is the comm important? Maybe add the function that called it?

    "%pS", _THIS_IP_

Perhaps add __always_inline, as _THIS_IP_ will point into the function
that calls this?

-- Steve


> +}
> +
> +static inline void
> +ratelimit_set_flags(struct ratelimit_state *rs, unsigned long flags)
> +{
> +	rs->flags = flags;
>  }
>  
>  extern struct ratelimit_state printk_ratelimit_state;
> diff --git a/lib/ratelimit.c b/lib/ratelimit.c
> index 2c5de86460c5..b753f0cfb00b 100644
> --- a/lib/ratelimit.c
> +++ b/lib/ratelimit.c
> @@ -46,12 +46,14 @@ int ___ratelimit(struct ratelimit_state *rs, const char *func)
>  		rs->begin = jiffies;
>  
>  	if (time_is_before_jiffies(rs->begin + rs->interval)) {
> -		if (rs->missed)
> +		if (rs->missed && !(rs->flags & RATELIMIT_MSG_ON_RELEASE))
>  			printk(KERN_WARNING "%s: %d callbacks suppressed\n",
>  				func, rs->missed);
>  		rs->begin   = jiffies;
>  		rs->printed = 0;
> -		rs->missed  = 0;
> +
> +		if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE))
> +			rs->missed = 0;
>  	}
>  	if (rs->burst && rs->burst > rs->printed) {
>  		rs->printed++;