linux-kernel - Re: [RESEND PATCH 0/11] kernel:lockdep:replace DFS with BFS

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Date:	Mon, 13 Jul 2009 11:16:14 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	tom.leiming@...il.com
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	mingo@...e.hu
Subject: Re: [RESEND PATCH 0/11] kernel:lockdep:replace DFS with BFS

On Sun, 2009-06-28 at 23:04 +0800, tom.leiming@...il.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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