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Date: Fri, 25 Jun 2010 11:23:33 +0200
Message-ID: <AANLkTikEpj6EkJJ2dWs12JiODF8pl4foYq_AZtzxP2ef@mail.gmail.com>
Subject: Re: [RFC][PATCH] irq_work
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Huang Ying <ying.huang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>,
       "H.PeterA" <"nvin hpa"@zytor.com>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       Andi Kleen <andi@firstfloor.org>
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2010/6/25 Huang Ying <ying.huang@intel.com>:
> On Fri, 2010-06-25 at 15:48 +0800, Peter Zijlstra wrote:
>> On Fri, 2010-06-25 at 10:12 +0800, Huang Ying wrote:
>> >
>> > It is better to add "void *data" field in this struct to allow same
>> > function can be used for multiple struct irq_work.
>>
>> No, simply do:
>>
>> struct my_foo {
>>   struct irq_work work;
>>   /* my extra data */
>> }
>>
>> void my_func(struct irq_work *work)
>> {
>>   struct my_foo *foo = container_of(work, struct my_foo, work);
>>
>>   /* tada! */
>> }
>
> Yes. This works too. But Adding "void *data" field is helpful if you do
> not embed struct irq_work into another struct.



That's what makes most sense. If you use work->data to put foo, then
you can also do the opposite. Now the best is to pick the choice that
gives you a real type and a typechecking, and not an error-prone and
obfuscated void *

This is the way things are made in the kernel. struct work_struct, struct list,
struct rcu_head, etc... are all embedded into a container, so that we can
use container_of.