linux-kernel - Re: [PATCH -mm resend] cpuhotplug: introduce try_get_online

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Message-ID: <4A30C346.8070406@cn.fujitsu.com>
Date:	Thu, 11 Jun 2009 16:41:42 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	paulmck@...ux.vnet.ibm.com
CC:	ego@...ibm.com, rusty@...tcorp.com.au, mingo@...e.hu,
	linux-kernel@...r.kernel.org, peterz@...radead.org,
	oleg@...hat.com, dipankar@...ibm.com
Subject: Re: [PATCH -mm resend] cpuhotplug: introduce try_get_online_cpus()
 take 3

Andrew Morton wrote:
> 
> I still think we should really avoid having to do this.  trylocks are
> nasty things.
> 
> Looking at the above, one would think that a correct fix would be to fix
> the bug in "thread 2": take the locks in the correct order?  As
> try_get_online_cpus() doesn't actually have any callers, it's hard to
> take that thought any further.
> 
> 

Sometimes, we can not reorder the locks' order.
try_get_online_cpus() is really needless when no one uses it.

Paul's expedited RCU V7 may need it:
http://lkml.org/lkml/2009/5/22/332

So this patch can be omitted when Paul does not use it.
It's totally OK for me.

Lai

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