linux-kernel - Re: [PATCH] Video : Amba: Use in_interrupt() in clcdfb

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Date:	Sun, 11 Mar 2012 19:47:27 +0530
From:	santosh prasad nayak <santoshprasadnayak@...il.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	FlorianSchandinat@....de, linux-fbdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] Video : Amba: Use in_interrupt() in clcdfb_sleep().

Not to use in_atomic()  in driver code.

 Following article  inspired me to do the change.
http://lwn.net/Articles/274695/

"in_atomic() is for core kernel use only. Because in special
circumstances (ie: kmap_atomic()) we run inc_preempt_count() even on
non-preemptible kernels to tell the per-arch fault handler that it was
invoked by copy_*_user() inside kmap_atomic(), and it must fail.
In other words, in_atomic() works in a specific low-level situation,
but it was never meant to be used in a wider context. Its placement in
hardirq.h next to macros which can be used elsewhere was, thus, almost
certainly a mistake. As Alan Stern pointed out, the fact that Linux
Device Drivers recommends the use of in_atomic() will not have helped
the situation. Your editor recommends that the authors of that book be
immediately sacked. "

In the present case, we just check whether its an IRQ context or user
context. So for that
we can use "in_interrupt()".

Greg also mentions the same in the following mail.
http://www.spinics.net/lists/newbies/msg43402.html

Regards
Santosh

On Sun, Mar 11, 2012 at 6:57 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Sun, Mar 11, 2012 at 06:44:25PM +0530, santosh nayak wrote:
>> From: Santosh Nayak <santoshprasadnayak@...il.com>
>>
>> Instead of "in_atomic()", we can use in_interrupt() to check whether
>> its an interrupt context.
>
> What are you trying to fix?
>
> Your description is an example of a bad commit comment.  It merely
> describes the change, which anyone can see by looking at the diff.
> What it totally and utterly fails to do is to describe _why_ the
> change is necessary or what the problem is.
>
> So, until it does, this patch gets a definite NAK.
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