* A simple question of a linux kernel beginner
@ 2013-10-31 11:31 韩磊
2013-10-31 11:57 ` Richard Weinberger
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: 韩磊 @ 2013-10-31 11:31 UTC (permalink / raw)
To: Linux Kernel Mailing List
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??
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: A simple question of a linux kernel beginner
2013-10-31 11:31 A simple question of a linux kernel beginner 韩磊
@ 2013-10-31 11:57 ` Richard Weinberger
2013-10-31 12:03 ` Levente Kurusa
2013-10-31 12:19 ` Yijing Wang
2013-10-31 18:13 ` Andreas Mohr
2 siblings, 1 reply; 6+ messages in thread
From: Richard Weinberger @ 2013-10-31 11:57 UTC (permalink / raw)
To: 韩磊; +Cc: Linux Kernel Mailing List
On Thu, Oct 31, 2013 at 12:31 PM, 韩磊 <bonben1989@gmail.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.
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
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--
Thanks,
//richard
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: A simple question of a linux kernel beginner
2013-10-31 11:57 ` Richard Weinberger
@ 2013-10-31 12:03 ` Levente Kurusa
0 siblings, 0 replies; 6+ messages in thread
From: Levente Kurusa @ 2013-10-31 12:03 UTC (permalink / raw)
To: Richard Weinberger, 韩磊; +Cc: Linux Kernel Mailing List
2013-10-31 12:57 keltezéssel, Richard Weinberger írta:
> On Thu, Oct 31, 2013 at 12:31 PM, 韩磊 <bonben1989@gmail.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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: A simple question of a linux kernel beginner
2013-10-31 11:31 A simple question of a linux kernel beginner 韩磊
2013-10-31 11:57 ` Richard Weinberger
@ 2013-10-31 12:19 ` Yijing Wang
2013-10-31 18:13 ` Andreas Mohr
2 siblings, 0 replies; 6+ messages in thread
From: Yijing Wang @ 2013-10-31 12:19 UTC (permalink / raw)
To: 韩磊; +Cc: Linux Kernel Mailing List
On 2013/10/31 19:31, 韩磊 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??
no float in kernel!
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
>
--
Thanks!
Yijing
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: A simple question of a linux kernel beginner
2013-10-31 11:31 A simple question of a linux kernel beginner 韩磊
2013-10-31 11:57 ` Richard Weinberger
2013-10-31 12:19 ` Yijing Wang
@ 2013-10-31 18:13 ` Andreas Mohr
2013-11-01 1:12 ` 韩磊
2 siblings, 1 reply; 6+ messages in thread
From: Andreas Mohr @ 2013-10-31 18:13 UTC (permalink / raw)
To: =?GB2312?B?uqvA2g==?=; +Cc: Linux Kernel Mailing List
Hi,
> May I can use the ''double" as a basic variables?
[see other replies]
Look into terminus technicus "scaling math" as a replacement technique
(in-kernel this is being used e.g. by clocksources/clockevents).
HTH,
Andreas Mohr
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: A simple question of a linux kernel beginner
2013-10-31 18:13 ` Andreas Mohr
@ 2013-11-01 1:12 ` 韩磊
0 siblings, 0 replies; 6+ messages in thread
From: 韩磊 @ 2013-11-01 1:12 UTC (permalink / raw)
To: Andreas Mohr; +Cc: Linux Kernel Mailing List
Thank you! I still have a long way to go in kernel.
2013/11/1 Andreas Mohr <andi@lisas.de>:
> Hi,
>
>> May I can use the ''double" as a basic variables?
>
> [see other replies]
>
>
> Look into terminus technicus "scaling math" as a replacement technique
> (in-kernel this is being used e.g. by clocksources/clockevents).
>
> HTH,
>
> Andreas Mohr
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2013-11-01 1:12 UTC | newest]
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2013-10-31 11:31 A simple question of a linux kernel beginner 韩磊
2013-10-31 11:57 ` Richard Weinberger
2013-10-31 12:03 ` Levente Kurusa
2013-10-31 12:19 ` Yijing Wang
2013-10-31 18:13 ` Andreas Mohr
2013-11-01 1:12 ` 韩磊
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