linux-kernel - Re: [PATCH 07/07] printk delay per multi lines

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Message-ID: <1267114634.22519.0.camel@laptop>
Date:	Thu, 25 Feb 2010 17:17:14 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Dave Young <hidave.darkstar@...il.com>
Cc:	Randy Dunlap <rdunlap@...otime.net>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Hans-Joachim Picht <hans@...ibm.com>,
	Simon Kagstrom <simon.kagstrom@...insight.net>,
	David Woodhouse <David.Woodhouse@...el.com>,
	James Morris <jmorris@...ei.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Catalin Marinas <catalin.marinas@....com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH 07/07] printk delay per multi lines

On Thu, 2010-02-25 at 23:45 +0800, Dave Young wrote:
> +               if (!atomic_read(&l))
> +                       atomic_set(&l, printk_delay_lines);

That's racy, use atomic_cmpxchg()

> +               smp_mb__before_atomic_dec();
> +               if (atomic_dec_return(&l))
> +                       return; 

What's that barrier for?

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