linux-kernel - Re: [PATCH -mm 1/2] irq_work, Use llist in irq

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Date:	Thu, 01 Sep 2011 11:57:15 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Huang Ying <ying.huang@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH -mm 1/2] irq_work, Use llist in irq_work

On Thu, 2011-09-01 at 16:56 +0800, Huang Ying wrote:
> Something as follow with llist_empty() seems not work.
> 
>   empty = llist_empty(irq_work_list);
>   llist_add(&work->llnode, irq_work_list);
>   if (empty)
>           arch_irq_work_raise();
> 
> Because irq_work IRQ handler or timer IRQ handler may be executed just
> before "llist_add(&work->llnode, irq_work_list)", so that, although
> "empty == false", arch_irq_work_raise() still should be executed.

Right, I was thinking:

	llist_add(&work->llist, irq_work_list);
	if (llist_empty(&work->llist))
		arch_irq_work_raise();

And then ran into the difference between llist_node and llist_head. Now
we could sort that by introducing llist_next() and write it like:

	if (!llist_next(&work->list))
		arch_irq_work_raise();


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