linux-kernel - Re: [RFC PATCH v5 1/2] Use lock_device_hotplug() in cpu_probe_store() and cpu_release

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Message-ID: <20140422204006.GA3615@mtj.dyndns.org>
Date:	Tue, 22 Apr 2014 16:40:06 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Li Zhong <zhong@...ux.vnet.ibm.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, gregkh@...uxfoundation.org,
	rafael.j.wysocki@...el.com, toshi.kani@...com
Subject: Re: [RFC PATCH v5 1/2] Use lock_device_hotplug() in
 cpu_probe_store() and cpu_release_store()

Hello,

On Tue, Apr 22, 2014 at 10:29:37AM +0800, Li Zhong wrote:
> The probe/release files are attribute files for cpu subsys, looks like
> following in sysfs dirs
> 
> $ cd /sys/devices/system/cpu/
> $ ls -l
> total 0
> drwxr-xr-x. 7 root root     0 Apr 17 19:00 cpu0
> drwxr-xr-x. 4 root root     0 Apr 17 19:00 cpu1
> drwxr-xr-x. 4 root root     0 Apr 17 19:00 cpu10
> ......
> drwxr-xr-x. 3 root root     0 Apr 20 08:00 cpufreq
> drwxr-xr-x. 2 root root     0 Apr 20 08:00 cpuidle
> -rw-------. 1 root root 65536 Apr 21 00:28 dscr_default
> -r--r--r--. 1 root root 65536 Apr 21 00:28 kernel_max
> -r--r--r--. 1 root root 65536 Apr 21 00:28 offline
> -r--r--r--. 1 root root 65536 Sep  4  2014 online
> -r--r--r--. 1 root root 65536 Apr 21 00:28 possible
> drwxr-xr-x. 2 root root     0 Apr 20 08:00 power
> -r--r--r--. 1 root root 65536 Apr 17 20:46 present
> --w-------. 1 root root 65536 Apr 21 00:28 probe        <-----	
> --w-------. 1 root root 65536 Apr 21 00:28 release      <-----
> -rw-------. 1 root root 65536 Apr 21 00:28 subcores_per_core
> -rw-r--r--. 1 root root 65536 Apr 21 00:28 uevent
> 
> From the code, it seems cpu subsys won't be unregistered, and it doesn't
> make sense to remove all the cpus in the system. 

I don't think I'm following you.  Are you saying that no files which
are protected under the hotplug lock that cpu subsys uses are removed
during offlining?

Thanks.

-- 
tejun
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