linux-kernel - Re: [PATCH RFC] v5 expedited "big hammer" RCU grace periods

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Message-ID: <4A110768.2040707@cn.fujitsu.com>
Date:	Mon, 18 May 2009 14:59:52 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	paulmck@...ux.vnet.ibm.com
CC:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org, mingo@...e.hu,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	davem@...emloft.net, dada1@...mosbay.com, zbr@...emap.net,
	jeff.chua.linux@...il.com, paulus@...ba.org, jengelh@...ozas.de,
	r000n@...0n.net, benh@...nel.crashing.org,
	mathieu.desnoyers@...ymtl.ca
Subject: Re: [PATCH RFC] v5 expedited "big hammer" RCU grace periods

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.

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