Subject: Re: [RESEND PATCH 0/11] kernel:lockdep:replace DFS with BFS
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: tom.leiming@gmail.com
Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, mingo@elte.hu
In-Reply-To: <1246201486-7308-1-git-send-email-tom.leiming@gmail.com>
References: <1246201486-7308-1-git-send-email-tom.leiming@gmail.com>
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Date: Mon, 13 Jul 2009 11:16:14 +0200
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On Sun, 2009-06-28 at 23:04 +0800, tom.leiming@gmail.com wrote:
> Hi,Peter
> 
> Currently lockdep uses recursion DFS(depth-first search) algorithm to
> search target in checking lock circle(check_noncircular()),irq-safe
> -> irq-unsafe(check_irq_usage()) and irq inversion when adding a new
> lock dependency. This patches replace the current DFS with BFS, based on
> the following consideration:
> 
>     1,no loss of efficiency, no matter DFS or BFS, the running time
>     are O(V+E) (V is vertex count, and E is edge count of one
>     graph);

I'd still like to get some feedback on the loss of that generation count
optimization done by DaveM, I haven't had time to analyze the
ramifications of that.

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