linux-kernel - Re: 回复: [PATCH v2] debugobjects: install cpu hotplug callback

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Message-ID: <87k0x94z40.fsf@nanos.tec.linutronix.de>
Date:   Fri, 04 Sep 2020 12:26:07 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Ingo Molnar <mingo@...nel.org>,
        "Zhang\, Qiang" <Qiang.Zhang@...driver.com>
Cc:     "longman\@redhat.com" <longman@...hat.com>,
        "elver\@google.com" <elver@...gle.com>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: 回复: [PATCH v2] debugobjects: install cpu
 hotplug callback

On Fri, Sep 04 2020 at 07:50, Ingo Molnar wrote:
>> +#if defined(CONFIG_HOTPLUG_CPU)
>> +static int object_cpu_offline(unsigned int cpu)
>> +{
>> +       struct debug_percpu_free *percpu_pool;
>> +       struct hlist_node *tmp;
>> +       struct debug_obj *obj;
>> +
>> +       percpu_pool = per_cpu_ptr(&percpu_obj_pool, cpu);
>> +       hlist_for_each_entry_safe(obj, tmp, &percpu_pool->free_objs, node) {
>> +               hlist_del(&obj->node);
>> +               kmem_cache_free(obj_cache, obj);
>> +       }
>> +
>> +       return 0;
>> +}
>> +#endif
>
> What happens to ->obj_free, if the CPU is brought back online? Won't it be 
> out of sync at that point?

Yes and it's going to do the completely wrong thing.

Thanks,

        tglx