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SubjectRe: [PATCH 2/3] stop_machine: dequeue work before signal completion
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Hi Tejun and Hillf,

On Wed, 6 Feb 2013 10:47:49 -0800, Tejun Heo wrote:
> On Wed, Feb 06, 2013 at 08:38:43PM +0800, Hillf Danton wrote:
>> As handled by the kernel thread, work is dequeued first for further actions.
>
> Ditto as the previous patch.
>
>> Signed-off-by: Hillf Danton <dhillf@gmail.com>
>> ---
>>
>> --- a/kernel/stop_machine.c Wed Feb 6 19:57:12 2013
>> +++ b/kernel/stop_machine.c Wed Feb 6 20:02:12 2013
>> @@ -334,23 +334,24 @@ static int __cpuinit cpu_stop_cpu_callba
>> #ifdef CONFIG_HOTPLUG_CPU
>> case CPU_UP_CANCELED:
>> case CPU_POST_DEAD:
>> - {
>> - struct cpu_stop_work *work;
>> -
>> sched_set_stop_task(cpu, NULL);
>> /* kill the stopper */
>> kthread_stop(stopper->thread);
>> /* drain remaining works */
>> spin_lock_irq(&stopper->lock);
>> - list_for_each_entry(work, &stopper->works, list)
>> + while (!list_empty(&stopper->works)) {
>> + struct cpu_stop_work *work;
>> + work = list_first_entry(&stopper->works,
>> + struct cpu_stop_work, list);
>> + list_del_init(&work->list);
>> cpu_stop_signal_done(work->done, false, 0);
>> + }
>> stopper->enabled = false;
>> spin_unlock_irq(&stopper->lock);
>
> Why does this matter? It's inside spinlock. What's being made better
> by this change?

IIUC the work should be deleted from the list, otherwise it'd trigger
BUG_ON when the cpu gets online again.

Thanks,
Namhyung


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