linux-kernel - Re: [PATCH 00/10] workqueue: restructure flush_workqueue() and start all flusher at the same time

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Date:	Tue, 25 Sep 2012 13:14:23 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/10] workqueue: restructure flush_workqueue() and
 start all flusher at the same time

Hello, Lai.

On Tue, Sep 25, 2012 at 05:02:31PM +0800, Lai Jiangshan wrote:
> I found the flush_workqueue() is not nature for me, especially

I don't think it's natural for anybody.  I'm not a big fan of that
code either.

> the usage of the colors and flush_workqueue_prep_cwqs().
> so I try to improve it without change too much things/behavior.
> 
> (These patchset delay other simple patches, I think I should
> send simple patches at first.)

Yes, please do so.

> I always check the code by hard reviewing the code. I always try to image
> there are many thread run in my brain orderless and I write all possible
> transitions in paper. This progress is the most important, no test can
> replace it.
> 
> Human brain can wrong, the attached patch is my testing code.
> It verify flush_workqueue() by cookie number.

Sure, nothing beats careful reviews but then again it's difficult to
have any level of confidence without actually excercising and
verifying each possible code path.  For tricky changes, it helps a lot
if you describe how the code was verified and why and how much you
feel confident about the change.

> I also need your testing code for workqueue. ^_^

Heh, you asked for it.  Attached.  It's a scenario based thing and I
use different scenarios usually in combination with some debug printks
to verify things are behaving as I think they should.

Thanks.

-- 
tejun

View attachment "test-wq.c" of type "text/x-csrc" (36403 bytes)