Re: [PATCH 10/43] stop_machine: reimplement without using workqueue
From: Tejun Heo
Date: Mon Mar 01 2010 - 10:12:27 EST
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?
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