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

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Message-ID: <d82e647a0905121728m278b604bn9a0f5122b964978a@mail.gmail.com>
Date:	Wed, 13 May 2009 08:28:15 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Cornelia Huck <cornelia.huck@...ibm.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>, arjan@...radead.org,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH] kernel/async.c:introduce async_schedule*_atomic

2009/5/13 Cornelia Huck <cornelia.huck@...ibm.com>:
> On Tue, 12 May 2009 18:52:29 +0200,
> Frederic Weisbecker <fweisbec@...il.com> wrote:
>
>> This division would make more sense indeed.
>>
>> - async_schedule_inatomic() would be nosync() and would use
>>   GFP_ATOMIC. I guess the case where we want to run
>>   a job synchronously from atomic in case of async failure is too rare
>>   (non-existent?).
>
> It would add complexity for those callers providing a function that is
> safe to be called in both contexts.
>
>> - async_schedule_nosync() would be only nosync() and would use
>>   GFP_KERNEL
>>
>> I'm not sure the second case will ever be used though.
>
> It might make sense for the "just fail if we cannot get memory" case.
>
>>
>> Another alternative would be to define a single async_schedule_nosync()
>> which also takes a gfp flag.
>
> Wouldn't async_schedule() then need a gfp flag as well?
>

IMHO, we should call async_schedule*() from non-atomic contexts and
async_schedule_inatomic*() from atomic contexts explicitly, so
async_schedule*()
use GFP_KERNEL and async_schedule_inatomic*() use GFP_ATOMIC
always. This can simplify the problem much more.

Also we still allow async_schedule*()  to run a job synchronously if
out of memory
or other failure. This can keep consistency with before.

Any sugesstions or objections?

-- 
Lei Ming
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