linux-kernel - Re: enable dynamic debug

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Message-ID: <CAHp75VfyjSEJhC7MKt7smniSfzPaF0KefVHO69DKFb89fk59RQ@mail.gmail.com>
Date:	Wed, 18 Nov 2015 21:12:21 +0200
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Muni Sekhar <munisekharrms@...il.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: enable dynamic debug - doubt

On Tue, Nov 17, 2015 at 2:40 PM, Muni Sekhar <munisekharrms@...il.com> wrote:
> [ Please keep me in CC as I'm not subscribed to the list]
>
>  Hello,
>
> The behaviour of dynamic debug prints are controlled via writing to a
> control file in the 'debugfs'
> filesystem(<debugfs>/dynamic_debug/control).
>
> Here I would like to know what order should the echo(for eg: echo -n
> 'module sdhci +p' > /sys/kernel/debug/dynamic_debug/control) be
> applied in relation to the module load - before or after?

Just imagine how debugfs works. It has probes over the code where
*_dbg/debug() prints are used. Those special data structures are kept
in the specific part of the file / kernel. If there is no module, how
will kernel know that there is a portion of such data there?

-- 
With Best Regards,
Andy Shevchenko
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