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From:   Waiman Long <longman@redhat.com>
To:     "Zhang, Qiang" <Qiang.Zhang@windriver.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
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Date:   Tue, 25 Aug 2020 19:32:40 -0400
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On 8/25/20 6:26 PM, Waiman Long wrote:
> On 8/25/20 12:53 AM, Zhang, Qiang wrote:
>> ________________________________________
>> ??????: linux-kernel-owner@vger.kernel.org 
>> <linux-kernel-owner@vger.kernel.org> ???? qiang.zhang@windriver.com 
>> <qiang.zhang@windriver.com>
>> ????ʱ??: 2020??8??20?? 11:24
>> ?ռ???: tglx@linutronix.de; elver@google.com; longman@redhat.com
>> ????: linux-kernel@vger.kernel.org
>> ????: [PATCH] debugobjects: install cpu hotplug callback
>>
>> From: Zqiang <qiang.zhang@windriver.com>
>>
>> When a cpu going offline, we should free objects in "percpu_obj_pool"
>> free_objs list which corresponding to this cpu.
>
> The percpu free object pool is supposed to be accessed only by that 
> particular cpu without any lock. Trying to access it from another cpu 
> can cause a race condition unless one can make sure that the offline 
> cpu won't become online in the mean time. There shouldn't be too many 
> free objects in the percpu pool. Is it worth the effort to free them? 

Or if you can make the to-be-offlined cpu free the debugobjs before it 
is offlined. That will work too.

Cheers,
Longman