Re: 回复: [PATCH] debugobjects: install cpu hotplug callback

[Waiman Long]

On 8/25/20 6:26 PM, Waiman Long wrote:
> On 8/25/20 12:53 AM, Zhang, Qiang wrote:
> > ________________________________________
> > 发件人: linux-kernel-owner@xxxxxxxxxxxxxxx 
> > <linux-kernel-owner@xxxxxxxxxxxxxxx> 代表 qiang.zhang@xxxxxxxxxxxxx 
> > <qiang.zhang@xxxxxxxxxxxxx>
> > 发送时间: 2020年8月20日 11:24
> > 收件人: tglx@xxxxxxxxxxxxx; elver@xxxxxxxxxx; longman@xxxxxxxxxx
> > 抄送: linux-kernel@xxxxxxxxxxxxxxx
> > 主题: [PATCH] debugobjects: install cpu hotplug callback
> >
> > From: Zqiang <qiang.zhang@xxxxxxxxxxxxx>
> >
> > 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