linux-kernel - Re: [PATCH v4 10/13] staging: lustre: lnet: lnet: checkpatch.pl fixes

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Date:	Fri, 22 May 2015 16:57:10 -0700
From:	Joe Perches <joe@...ches.com>
To:	"Drokin, Oleg" <oleg.drokin@...el.com>
Cc:	Julia Lawall <Julia.Lawall@...6.fr>,
	Michael Shuey <shuey@...due.edu>,
	"<devel@...verdev.osuosl.org>" <devel@...verdev.osuosl.org>,
	"<gregkh@...uxfoundation.org>" <gregkh@...uxfoundation.org>,
	"<kernel-janitors@...r.kernel.org>" <kernel-janitors@...r.kernel.org>,
	"<linux-kernel@...r.kernel.org>" <linux-kernel@...r.kernel.org>,
	"<HPDD-discuss@...1.01.org>" <HPDD-discuss@...1.01.org>,
	"<lustre-devel@...ts.lustre.org>" <lustre-devel@...ts.lustre.org>
Subject: Re: [PATCH v4 10/13] staging: lustre: lnet: lnet: checkpatch.pl
 fixes

On Fri, 2015-05-22 at 21:16 +0000, Drokin, Oleg wrote:
> On May 22, 2015, at 11:42 AM, Joe Perches wrote:
> 
> > On Fri, 2015-05-22 at 08:08 +0000, Drokin, Oleg wrote:
> >> On May 22, 2015, at 1:06 AM, Julia Lawall wrote:
> >> 
> >>> On Thu, 21 May 2015, Michael Shuey wrote:
> >>> 
> >>>> That's a task (of many) I've been putting on the back burner until the code
> >>>> is cleaner.  It's also a HUGE change, since there are debug macros
> >>>> everywhere, and they all check a #define'd mask to see if they should fire,
> >>>> and the behavior is likely governed by parts of the lustre user land tools
> >>>> as well.
> >>>> 
> >>>> Suggestions are welcome.  Do other parts of the linux kernel define complex
> >>>> debugging macros like these, or is this a lustre-ism?  Any suggestions on
> >>>> how to handle this more in line with existing drivers?
> >>> 
> >>> Once you decide what to do, you can use Coccinelle to make the changes for
> >>> you.  So you shouldn't be put off by the number of code sites to change.
> >>> 
> >>> The normal functions are pr_err, pr_warn, etc.  Perhaps you can follow
> >>> Joe's suggestions if you really need something more complicated.
> >> 
> >> Ideally leaving CERROR/CDEBUG in Lustre would be desirable from my perspective.
> > 
> > My issue with CERROR is the name is little misleading.
> > It's actually a debugging message.
> > #define CERROR(format, ...)  CDEBUG_LIMIT(D_ERROR, format, ## __VA_ARGS__)
> 
> Except it's not a debugging message.
> There is a clear distinction.

Not really.  If the first reading sjows that the mechanism it
goes through is called CDEBUG, a reasonable expectation should
be that it's a debugging message.

> CERROR is something that get's printed on the console, because it's believed
> to be serious error (At least that's how the theory for it's usage goes).
> It also gets rate-limited so that the console does not get overflown.
> (but the debug buffer gets the full version).
> (there's also LCONSOLE that always get's printed, but it does not get the
> prefixes like line numbers and stuff).
> 
> CDEBUG on the other hand is a debugging message (of which ERROR messages are
> sort of a subset (D_ERROR mask)). You can fine-tune those to be noops or
> to go into console or to debug buffer only. Most of those are doing nothing
> because they are off in the default debug mask, until actually enabled.
> 
> That CERROR usees CDEBUG underneath is just to share some common infrastructure.
> 
> > I think it'd be clearer as
> > 	lustre_debug(ERROR, ...
> > even if the name and use style is a little longer.
> 
> I wonder what is more clear about that in your opinion ve
> lustre_error/lustre_debug?

The fact that you have to explain this shows that it's
at least misleading unless you completely understand the
code.

It'd be more intelligible if this CERROR became lustre_err
and the actual debugging uses were lustre_dbg

Perhaps it needs a better explanation somewhere not in the
code but in some external documentation.  I haven't looked.

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