netdev - Re: [RFC PATCH] net: NETDEV WATCHDOG should print something every time

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Date:	Sat, 23 Jan 2010 01:51:32 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Jesse Brandeburg <jesse.brandeburg@...el.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] net: NETDEV WATCHDOG should print something every
 time

On Fri, 2010-01-22 at 13:43 -0800, Jesse Brandeburg wrote:
> commit 5337407c changed NETDEV WATCHDOG messages into a message
> that will only print once per driver load.  This removed a significant amount
> of information from an admin who might be missing that his system was having
> NETDEV WATCHDOGs, esp since there is no other global counter available to
> count these events.
> 
> simply check the __warned flag and print a simple version of the message
> without the full stack dump if the (kerneloops related) WARN_ON_ONCE has
> already logged the hardware type and one hang.
[...]
> diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
> index 18c435d..ad810a0 100644
> --- a/include/asm-generic/bug.h
> +++ b/include/asm-generic/bug.h
> @@ -132,6 +132,11 @@ extern void warn_slowpath_null(const char *file, const int line);
>  	unlikely(__ret_warn_once);				\
>  })
>  
> +#define WARNED_ALREADY() ({					\
> +	static bool __warned;					\
> +	unlikely(__warned);					\
> +})

It is indeed unlikely that __warned will be true, given there is no
statement to set it...

I think this could be a generic macro:

#define first_time() ({						\
	static bool __been_here;				\
	__been_here++;						\
})

>  #define WARN_ON_RATELIMIT(condition, state)			\
>  		WARN_ON((condition) && __ratelimit(state))
>  
> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
> index 5173c1e..28fb14f 100644
> --- a/net/sched/sch_generic.c
> +++ b/net/sched/sch_generic.c
> @@ -251,8 +251,13 @@ static void dev_watchdog(unsigned long arg)
>  
>  			if (some_queue_timedout) {
>  				char drivername[64];
> -				WARN_ONCE(1, KERN_INFO "NETDEV WATCHDOG: %s (%s): transmit queue %u timed out\n",
> -				       dev->name, netdev_drivername(dev, drivername, 64), i);
> +				/* FIXME: is there a way to const char string[] = "NETDEV WATCHDOG..." */
[...]

Maybe you could, you know, just write that declaration... though a
'static' in front wouldn't hurt.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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