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

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Message-ID: <CAOD=uF5GbsyHS5iXjJ1YcqJyGLHwT8Wjhiie1daJAVqu527Umg@mail.gmail.com>
Date:	Sun, 11 Mar 2012 20:18:32 +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().

On Sun, Mar 11, 2012 at 8:06 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Sun, Mar 11, 2012 at 07:47:27PM +0530, santosh prasad nayak wrote:
>> 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
>
> In which case, we'll just have to do mdelay() and forget about allowing
> anything else to run for the 20ms that we need to sleep.  Sucky but
> that's the way things are.

 mdelay() or msleep() are there before. I did not change that.


my point is :  in_atomic()  vs "in_interrupt()".
We should avoid to use "in_atomic()" in driver code.

In the present case to check IRQ context "in_interrupt()" should be preferred.


regards
Santosh

regards
Santosh
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