linux-kernel - Re: [PATCH 5/5] ring-buffer: fix printk output

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Message-ID: <20090429201555.GG17021@elte.hu>
Date:	Wed, 29 Apr 2009 22:15:55 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Valdis.Kletnieks@...edu
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 5/5] ring-buffer: fix printk output


* Valdis.Kletnieks@...edu <Valdis.Kletnieks@...edu> wrote:

> On Tue, 28 Apr 2009 23:20:00 PDT, Andrew Morton said:
> > printk_once() is racy on smp and preempt btw ;)
> 
> Looks like at worst, it's prone to the usual printk racing, plus a 
> possible misfire causing it to print twice before shutting up?  Or 
> is there something I'm missing here?

Yeah, that's the worst-case scenario.

Still worth improving if we can do it without bloating the code or 
data.

[ If not, we can just assume the kernel is perfect and ignore all
  the printk_once() and WARN_ONCE() / WARN_ON_ONCE() callsites as
  obviously dead code ;-) ]

	Ingo
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