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From: Waiman Long <longman@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	"Zhang, Qiang" <Qiang.Zhang@windriver.com>,
	"elver@google.com" <elver@google.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>
Subject: Re: 回复: [PATCH] debugobjects: install cpu hotplug callback
Date: Tue, 25 Aug 2020 20:48:53 -0400	[thread overview]
Message-ID: <eedc945f-2d48-1dcf-30f3-21e2e1b094f9@redhat.com> (raw)
In-Reply-To: <87pn7ewae6.fsf@nanos.tec.linutronix.de>

On 8/25/20 7:53 PM, Thomas Gleixner wrote:
> On Tue, Aug 25 2020 at 18:26, Waiman Long wrote:
>> On 8/25/20 12:53 AM, Zhang, Qiang wrote:
>>> 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.
> It is actually safe because CPU hotplug is globally serialized and there
> is no way that an offline CPU will come back from death valley
> magically. If such a zombie ever surfaces then we have surely more
> serious problems than accessing that pool :)

Thanks for the clarification. I haven't looked into where the callback 
functions are being called so I am not 100% sure.

Cheers,
Longman


  reply	other threads:[~2020-08-26  0:49 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-20  3:24 qiang.zhang
2020-08-25  4:53 ` 回复: " Zhang, Qiang
2020-08-25 22:26   ` Waiman Long
2020-08-25 23:32     ` Waiman Long
2020-08-25 23:53     ` Thomas Gleixner
2020-08-26  0:48       ` Waiman Long [this message]
2020-08-26  8:34       ` 回复: " Zhang, Qiang
2020-08-26  9:41         ` Thomas Gleixner

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