linux-kernel - Re: [PATCH] kmsg_dump: Don't run on non-error paths by default

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Message-ID: <20120208163007.GA19323@redhat.com>
Date:	Wed, 8 Feb 2012 11:30:07 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Matthew Garrett <mjg@...hat.com>
Cc:	linux-kernel@...r.kernel.org, seiji.aguchi@....com,
	dzickus@...hat.com
Subject: Re: [PATCH] kmsg_dump: Don't run on non-error paths by default

On Wed, Feb 08, 2012 at 11:14:06AM -0500, Matthew Garrett wrote:

[..]
> +/*
> + * Keep this list arranged in rough order of priority. Anything listed after
> + * KMSG_DUMP_OOPS will not be logged by default unless printk.always_kmsg_dump
> + * is passed to the kernel.
> + */
>  enum kmsg_dump_reason {
> -	KMSG_DUMP_OOPS,
>  	KMSG_DUMP_PANIC,
> +	KMSG_DUMP_OOPS,
> +	KMSG_DUMP_EMERG,
>  	KMSG_DUMP_RESTART,
>  	KMSG_DUMP_HALT,
>  	KMSG_DUMP_POWEROFF,
> -	KMSG_DUMP_EMERG,
>  };
>  
>  /**
> diff --git a/kernel/printk.c b/kernel/printk.c
> index 13c0a11..e7d07f5 100644
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
> @@ -702,6 +702,9 @@ static bool printk_time = 0;
>  #endif
>  module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
>  
> +static bool always_kmsg_dump;
> +module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
> +
>  /* Check if we have any console registered that can be called early in boot. */
>  static int have_callable_console(void)
>  {
> @@ -1732,6 +1735,9 @@ void kmsg_dump(enum kmsg_dump_reason reason)
>  	unsigned long l1, l2;
>  	unsigned long flags;
>  
> +	if (reason > KMSG_DUMP_PANIC && !always_kmsg_dump)
> +		return;

Did you mean reason > KMSG_DUMP_OOPS to enable oops logging by default?
 
Given the fact that not everybody likes kmsg_dump() and it is not known
how stable it with various backends, will it make sense to keep it disabled
by default and provide a knob to enable it (instead of always_kmsg_dump).

Thanks
Vivek
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