Re: [PATCH] fix-flush_workqueue-vs-cpu_dead-race-update

[Oleg Nesterov <oleg@tv-sign.ru>]

On 01/07, Oleg Nesterov wrote:
> 
> How about:
> 
> 	CPU_DEAD does nothing. After __cpu_disable() cwq->thread runs on
> 	all CPUs and becomes idle when it flushes cwq->worklist: nobody
> 	will add work_struct on that list.

Also, we can add cpu_workqueue_struct->should_exit_after_flush flag, but
we have to be careful to serialize with destroy_workqueue/CPU_UP.

> 	CPU_UP:
> 		if (!cwq->thread)
> 			create_workqueue_thread();
> 		else
> 			set_cpus_allowed(newcpu);
> 
> 	flush_workqueue:
> 		for_each_possible_cpu()		// NOT online!
> 			if (cwq->thread)
> 				flush_cpu_workqueue()

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