linux-kernel - Re: A simple question of a linux kernel beginner

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Message-ID: <52724712.6020809@linux.com>
Date:	Thu, 31 Oct 2013 13:03:30 +0100
From:	Levente Kurusa <levex@...ux.com>
To:	Richard Weinberger <richard.weinberger@...il.com>,
	韩磊 <bonben1989@...il.com>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: A simple question of a linux kernel beginner

2013-10-31 12:57 keltezéssel, Richard Weinberger írta:
> On Thu, Oct 31, 2013 at 12:31 PM, 韩磊 <bonben1989@...il.com> wrote:
>> May I can use  the ''double" as a  basic variables?
>>
>> When I define the "double" as a function return type in linux kernel,the error
>> is "error: SSE register return with SSE disabled".
>>
>> How to fix it??
> 
> Don't do it. :)
> In kernel land we don't want FPU stuff because it slows the mode switch down.
> If you *really* need to use the FPU look how the raid6 or crypto code does.

Not only it slows down the switches, but if there is no FPU, then it would
need the so-called floating-point-library. Which would slow down the code,
but the kernel needs to be as fast as it can.

-- 
Regards,
Levente Kurusa
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