From mboxrd@z Thu Jan  1 00:00:00 1970
From: Lai Jiangshan <laijs@cn.fujitsu.com>
Subject: Re: [PATCH RFC] v5 expedited "big hammer" RCU grace periods
Date: Mon, 18 May 2009 14:59:52 +0800
Message-ID: <4A110768.2040707@cn.fujitsu.com>
References: <20090517191141.GA25915@linux.vnet.ibm.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	netfilter-devel@vger.kernel.org, mingo@elte.hu,
	akpm@linux-foundation.org, torvalds@linux-foundation.org,
	davem@davemloft.net, dada1@cosmosbay.com, zbr@ioremap.net,
	jeff.chua.linux@gmail.com, paulus@samba.org, jengelh@medozas.de,
	r000n@r000n.net, benh@kernel.crashing.org,
	mathieu.desnoyers@polymtl.ca
To: paulmck@linux.vnet.ibm.com
Return-path: <netfilter-devel-owner@vger.kernel.org>
Received: from cn.fujitsu.com ([222.73.24.84]:60243 "EHLO song.cn.fujitsu.com"
	rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP
	id S1755609AbZERHCO (ORCPT <rfc822;netfilter-devel@vger.kernel.org>);
	Mon, 18 May 2009 03:02:14 -0400
In-Reply-To: <20090517191141.GA25915@linux.vnet.ibm.com>
Sender: netfilter-devel-owner@vger.kernel.org
List-ID: <netfilter-devel.vger.kernel.org>

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.