Subject: Re: [PATCH RFC] v5 expedited "big hammer" RCU grace periods

From: Lai Jiangshan <[email-masked]>
Date: Mon, 18 May 2009 14:59:52 +0800

Paul E. McKenney wrote:
> +void sched_expedited_wake(void *unused)
> +{
> +	mutex_lock(&__get_cpu_var(sched_expedited_done_mutex));
> +	if (__get_cpu_var(sched_expedited_done_qs) ==
> +	    SCHED_EXPEDITED_QS_DONE_QS) {
> +		__get_cpu_var(sched_expedited_done_qs) =
> +			SCHED_EXPEDITED_QS_NEED_QS;
> +		wake_up(&__get_cpu_var(sched_expedited_qs_wq));
> +	}
> +	mutex_unlock(&__get_cpu_var(sched_expedited_done_mutex));
> +}

[...]

> +		get_online_cpus();
> +		preempt_disable();
> +		mycpu = smp_processor_id();
> +		smp_call_function(sched_expedited_wake, NULL, 1);

sched_expedited_wake() calls mutex_lock() which may sleep?

And I think you have re-implement workqueue.

Thanks, Lai.