linux-kernel - Re: On "ratelimit: Use per ratelimit context locking"

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Message-ID: <4B3961B4.9000405@s5r6.in-berlin.de>
Date:	Tue, 29 Dec 2009 02:56:04 +0100
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Jay Fenlason <fenlason@...hat.com>
Subject: Re: On "ratelimit: Use per ratelimit context locking"

Ingo Molnar wrote:
> There used to be a global lock:
> 
>   static DEFINE_SPINLOCK(ratelimit_lock);
> 
> which is now per ratelimit context. The case i was after was to use the 
> ratelimit state from NMI context. With NMIs we can lock up if an NMI hits when 
> some other code uses the ratelimit code. It's a small but existing race 
> window.

Ah, I see.

> OTOH, IRQ context use of printk ratelimit was safe before (and after) this 
> commit - so i think your code should be safe too.

Thanks for the explanation; that's reassuring.
-- 
Stefan Richter
-=====-==--= ==-- ===-=
http://arcgraph.de/sr/
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