linux-kernel - Re: [PATCH v2 1/1] headers: fix circular dependency between linux/sched.h and linux/wait.h

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Date:	Mon, 21 Feb 2011 18:03:18 +0200
From:	David Cohen <dacohen@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu,
	linux-omap@...r.kernel.org, linux-media@...r.kernel.org,
	Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: [PATCH v2 1/1] headers: fix circular dependency between
 linux/sched.h and linux/wait.h

On Mon, Feb 21, 2011 at 5:54 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Mon, 2011-02-21 at 16:38 +0200, David Cohen wrote:
>> Currently sched.h and wait.h have circular dependency between both.
>> wait.h defines macros wake_up*() which use macros TASK_* defined by
>> sched.h. But as sched.h indirectly includes wait.h, such wait.h header
>> file can't include sched.h too. The side effect is when some file
>> includes wait.h and tries to use its wake_up*() macros, it's necessary
>> to include sched.h also.
>> This patch moves all TASK_* macros from linux/sched.h to a new header
>> file linux/task_state.h. This way, both sched.h and wait.h can include
>> task_state.h and fix the circular dependency. No need to include sched.h
>> anymore when wake_up*() macros are used.
>
> I think Alexey already told you what you done wrong.
>
> Also, I really don't like the task_state.h header, it assumes a lot of
> things it doesn't include itself and only works because its using macros
> and not inlines at it probably should.

Like wait.h I'd say. The main issue is wait.h uses TASK_* macros but
cannot properly include sched.h as it would create a circular
dependency. So a file including wait.h is able to compile because the
dependency of sched.h relies on wake_up*() macros and it's not always
used.
We can still drop everything else from task_state.h but the TASK_*
macros and then the problem you just pointed out won't exist anymore.
What do you think about it?

Br,

David

>
>
>
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