linux-kernel - Re: [PATCH 1/4] Dynamic Debug: Introduce global fake module param module.ddebug

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Message-Id: <201010062340.53041.trenn@suse.de>
Date:	Wed, 6 Oct 2010 23:40:52 +0200
From:	Thomas Renninger <trenn@...e.de>
To:	Greg KH <greg@...ah.com>
Cc:	gregkh@...e.de, linux-kernel@...r.kernel.org, bjorn.helgaas@...com,
	jbaron@...hat.com
Subject: Re: [PATCH 1/4] Dynamic Debug: Introduce global fake module param module.ddebug - V4

On Wednesday 06 October 2010 11:16:04 pm Greg KH wrote:
> On Fri, Sep 24, 2010 at 02:28:28PM +0200, Thomas Renninger wrote:
> > Dynamic Debug allows enabling of pr_debug and dev_dbg messages at
> > runtime. This is controlled via /sys/kernel/debug/dynamic_debug/control.
> > One major drawback is that the whole initialization of a module cannot be
> > tracked, because ddebug is only aware of debug strings of loaded modules.
> > But this is the most interesting part...
> >
> > This patch introduces a fake module parameter module.ddebug(not shown in
> > /sys/module/*/parameters, thus it does not use any resources/memory).
> >
> > If a module passes ddebug as a module parameter (e.g. via module.ddebug
> > kernel boot param or via "modprobe module ddebug"), all debug strings of
> > this module get activated by issuing "module module_name +p" internally
> > (not via sysfs) when the module gets loaded.
> >
> > Possible enhancements for the future if ddebug might get extended with
> > further flags:
> > module.ddebug=flags
> > Then module.ddebug="p" would be the same as module.ddebug, but if there
> > is a "x" ddebug flag added, one could pass:
> > module.ddebug="xp"
> > which would result in such a dynamic debug query:
> > module module_name +xp
> >
> > Modules must not use "ddebug" as module parameter or it will get ignored.
> > If it's tried, a warning will show up at module load time that it will
> > get ignored (only works for not built-in modules).
> >
> > Tested with (additional added pr_debug messages):
> > options hp-wmi ddebug
> > in modprobe.conf
> > -> works and pr_debug messages issued at module initialization time show
> > up. Also "p" flag gets set for the whole hp-wmi module:
> > grep hp-wmi /sys/../dynamic_debug/control
> > also tested with compiled-in modules, e.g. pnp.ddebug and an additional
> > patch later in the patch series which instruments pnp code to work with
> > ddebug.
>
> I don't think you actually built this patch, as it dies:
> kernel/params.c: In function ‘parse_one’:
> kernel/params.c:114:2: error: ‘tmp’ undeclared (first use in this function)
> kernel/params.c:114:2: note: each undeclared identifier is reported only
> once for each function it appears in kernel/params.c: In function
> ‘destroy_params’:
> kernel/params.c:726:8: warning: unused variable ‘tmp’
Strange, I added them to the latest SUSE factory kernel already and I didn't 
do much more than copying (and slightly adjusting?).

Can you give me a pointer to your git tree and branch you want the
patches based on, iirc I based them on latest Linus master branch.

Sorry and thanks,

      Thomas
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