netdev - Re: [PATCH v2] dynamic_debug: Restore dev_dbg functionality, optimize stack

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Date:	Tue, 31 Jul 2012 14:55:34 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Joe Perches <joe@...ches.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Jason Baron <jbaron@...hat.com>,
	Jim Cromie <jim.cromie@...il.com>, Kay Sievers <kay@...y.org>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2] dynamic_debug: Restore dev_dbg functionality,
 optimize stack

On Sat, 28 Jul 2012 00:55:07 -0700
Joe Perches <joe@...ches.com> wrote:

> commit c4e00daaa9 ("driver-core: extend dev_printk() to pass structured data")
> changed __dev_printk and broke dynamic-debug's ability to control the
> dynamic prefix of dev_dbg(dev,..).
> 
> dynamic_emit_prefix() adds "[tid] module:func:line:" to the output and
> those additions got lost.
> 
> In addition, the current dynamic debug code uses up to 3 recursion
> levels via %pV.  This can consume quite a bit of stack.  Directly
> call printk_emit to reduce the recursion depth.
> 
> These changes include:
> 
> o Remove KERN_DEBUG from dynamic_emit_prefix
> o Create and use function create_syslog_header to format the syslog
>   header for printk_emit uses.
> o Call create_syslog_header and neaten __dev_printk
> o Call create_syslog_header and printk_emit from dynamic_dev_dbg
> o Call create_syslog_header and printk_emit from dynamic_netdev_dbg
> o Make __dev_printk and __netdev_printk static not global
> o Remove include header declarations of __dev_printk and __netdev_printk
> o Remove now unused EXPORT_SYMBOL()s of __dev_printk and __netdev_printk
> o Whitespace neatening
> 
> Changes in v2:
> 
> o Fix dynamic_emit_prefix to always initialize output
> o Call create_syslog_header and emit_printk from__netdev_printk and
>   eliminate call to dev_printk to remove another recursion via %pV

This one causes an oops-on-boot
(http://ozlabs.org/~akpm/stuff/IMG_20120731_144047.jpg).  v1 didn't do
that.

config: http://ozlabs.org/~akpm/stuff/config-akpm2
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