linux-kernel - Question with maxcpus= parameter.

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Message-ID: <563C3980.8060405@oracle.com>
Date:	Fri, 6 Nov 2015 13:24:16 +0800
From:	Zhenzhong Duan <zhenzhong.duan@...cle.com>
To:	rusty@...tcorp.com.au, ashok.raj@...el.com,
	LKML <linux-kernel@...r.kernel.org>
Cc:	Feng Jin <joe.jin@...cle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: Question with maxcpus= parameter.

Hi Maintainers,

Recently we faced an cpu online issue with maxcpus= parameter.

We want to have 4 cpus onlined at bootup, test 3.8.13-stable on an 72 
cpus env with maxcpus=4, I found more cpus than 4 are onlined.
It's the udev scripts make them onlined. But below script exist for a 
long time.
ACTION=="add", KERNEL=="cpu[0-9]*", RUN+="/bin/bash -c 'echo 1 > 
/sys/devices/system/cpu/%k/online'"

maxcpu= parameter didn't take effect, so is this a kernel bug? Or that 
script should be removed?

Btw: 2.6.39 works fine, I checked udev log, seems CPU ADD event is only 
sent for 4cpus.
Why the difference between 2.6.39 and 3.8.13?

thanks
zduan
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