linux-kernel - Re: [patch] oom: change warning for deprecated oom_adj to avoid WARN

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Message-ID: <20110804074820.GA22842@liondog.tnic>
Date:	Thu, 4 Aug 2011 09:48:21 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch] oom: change warning for deprecated oom_adj to avoid
 WARN_ONCE()

On Wed, Aug 03, 2011 at 11:04:55PM -0700, David Rientjes wrote:
> > > -	WARN_ONCE(1, "%s (%d): /proc/%d/oom_adj is deprecated, please use /proc/%d/oom_score_adj instead.\n",
> > > -		  current->comm, task_pid_nr(current), task_pid_nr(task),
> > > -		  task_pid_nr(task));
> > > +	if (!warning_printed) {
> > > +		warning_printed = true;
> > > +		printk("\n===============================================================================\n");
> > > +		printk("%s (%d): /proc/%d/oom_adj is deprecated, please use /proc/%d/oom_score_adj instead.\n",
> > > +			current->comm, task_pid_nr(current), task_pid_nr(task),
> > > +			task_pid_nr(task));
> > > +		printk("===============================================================================\n\n");
> > 
> > You're missing the KERN_WARNING level.
> 
> It's intentional because (i) I'm using a multi-line notification with 
> newlines and (ii) I don't want to be considered as a kernel warning.  It's 
> just for consumption by userspace and doesn't indicate a kernel issue.

I see.

> > Why don't you use pr_warn_once +
> > pr_cont_once? No need for the warning_printed too, it gets defined in
> > another scope by the pr_warn_once macro automatically.
> > 
> 
> Because using pr_warn_once + pr_cont_once for a multi-line notification is 
> racy and I don't want three separated static variables?  pr_cont_once() 
> shouldn't be used unless synchronized.

Or maybe do:

	pr_info_once("\n===============================================================================\n"
		     "%s (%d): /proc/%d/oom_adj is deprecated, please use /proc/%d/oom_score_adj instead.\n"
		     "===============================================================================\n\n",
		     current->comm, task_pid_nr(current), task_pid_nr(task), task_pid_nr(task));

so as to not be a warning and still hide the warning_printed thing. You
could even save yourself the last repeated argument by enumerating the
format specifiers:

	pr_info_once("\n===============================================================================\n"
		     "%1$s (%2$d): /proc/%3$d/oom_adj is deprecated, please use /proc/%3$d/oom_score_adj instead.\n"
		     "===============================================================================\n\n",
		     current->comm, task_pid_nr(current), task_pid_nr(task));

It seems to build fine here.

Oh well. :-)

-- 
Regards/Gruss,
    Boris.
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