Re: [PATCH 10/43] stop_machine: reimplement without using workqueue

[Tejun Heo]

Hello, again.

On 02/28/2010 11:34 PM, Oleg Nesterov wrote:
> On 02/26, Tejun Heo wrote:
>>
>> @@ -164,19 +259,18 @@ int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
>>  	idle.fn = chill;
>>  	idle.data = NULL;
>>
>> +	smp_wmb();			/* -> stop_cpu()::set_current_state() */
>> ...
>> +	for_each_online_cpu(i)
>> +		wake_up_process(*per_cpu_ptr(stop_machine_threads, i));
> 
> Afaics, this smp_wmb() is not needed, wake_up_process() (try_to_wake_up)
> should ensure we can't race with set_current_state() + check_condition.
> It does, note the wmb() in try_to_wake_up().

Yeap, the initial version was like that and it was awkward to explain
in the comment in stop_cpu() so I basically put it there as a
documentation anchor.  Do you think removing it would be better?

Thanks.

-- 
tejun
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