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

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Date:	Thu, 16 Jul 2009 12:39:06 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>, mingo@...e.hu
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [RESEND PATCH 0/11] kernel:lockdep:replace DFS with BFS

2009/7/13 Peter Zijlstra <a.p.zijlstra@...llo.nl>:
> 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.
>
>

Hi, Ingo and Peter

As you said, BFS patch-set is valuable(decrease kernel stack consume
largely, and report
the shortest circle).

It has been pending on lkml silently for several monthes, and I hope
it may be merged to
tip-tree or other tree. I don't know what we should and can do to make
it being accepted by tip-tree.
Anyway, I'd like to do any fixes for it to be merged.

Any suggestions, ideas or objections?

Thanks.

-- 
Lei Ming
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