linux-kernel - Re: [PATCH] kernel/async.c:introduce async_schedule*

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Date:	Mon, 18 May 2009 09:55:14 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH] kernel/async.c:introduce async_schedule*_atomic

2009/5/18 Arjan van de Ven <arjan@...radead.org>:
> On Tue, 12 May 2009 23:13:42 +0800
> tom.leiming@...il.com wrote:
>
>> From: Ming Lei <tom.leiming@...il.com>
>>
>> The async_schedule* may not be called in atomic contexts if out of
>> memory or if there's too much work pending already, because the
>> async function to be called may sleep.
>>
>> This patch fixes the comment of async_schedule*, and introduces
>> async_schedules*_atomic to allow them called from atomic contexts
>> safely.
>
> (sorry for the late response; have been away from most of my email for
> a few days)
>
> I like the general idea; I was hoping to do it a little bit different
> though, API wise.
> I don't mind the parameter for "don't do blocking things" (we should
> use that to also use GFP_KERNEL/GFP_NOFS or whatever for the
> allocation), it makes sense.
>
> What I would like to see is the option to pass in memory that was
> externally kmalloc'd. So that you can do
>
> foo = kmalloc(..)
> spin_lock(bar)
> ...
> async_schedule_atomic(...);
>
> spin_unlock(bar);
> if (not_used_foo)
>    kfree(foo);
>
> in cases where you don't want to fail while in the atomic portion,
> but can fail better earlier.

If we do this way, the type of async_schedule*()  and async_schedule*_inatomic()
is different, and callers will be messed with them, especially for _inatomic().

BTW: I have submited new version of this patches, would you mind
giving a review?

Thanks.

-- 
Lei Ming
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