From: Jan Kiszka <jan.kiszka@siemens.com>
To: Richard Weinberger <richard.weinberger@gmail.com>
Cc: Xenomai <xenomai@xenomai.org>
Subject: Re: rt_task_shadow() secondary mode
Date: Thu, 8 Jul 2021 12:20:32 +0200 [thread overview]
Message-ID: <de2ec266-451f-8a49-380b-da46c1e4adda@siemens.com> (raw)
In-Reply-To: <CAFLxGvyn5SdGr8v8tNGCh8w7ciJLwY2wgLVsqiyxkBNXJvmVHg@mail.gmail.com>
On 08.07.21 12:04, Richard Weinberger wrote:
> On Thu, Jul 8, 2021 at 11:54 AM Jan Kiszka <jan.kiszka@siemens.com> wrote:
>>
>> On 08.07.21 11:51, Richard Weinberger wrote:
>>> On Thu, Jul 8, 2021 at 11:25 AM Jan Kiszka <jan.kiszka@siemens.com> wrote:
>>>> The general philosophy of Xenomai is that applications should not rely
>>>> on the exact switching behavior. So the question would be why your
>>>> application needs one or the other behavior?
>>>
>>> In this particular case the application uses the ioctl() system call
>>> to call into a
>>> xenomai kernel module. The module implements the rt and nrt variant of
>>> ioctl() and
>>> the application assumes which version of the ioctl() implementation
>>> will get reached.
>>
>> ...that might be the actual design bug. If a driver implements the a
>> service for both calling modes, the service should effectively do the
>> same, ie. should be mode-agnostic. Seems, this was violated here.
>
> Can be, the driver was designed a long time ago. :-)
> In the nrt ioctl() the driver uses e.g. ioremap(), this cannot work in primary
> mode. Is the desired approach switching to secondary mode when in primary
> mode such a code path is to be executed?
>
Correct. That is easily achieved by returning -ENOSYS from the rt
handler when seeing that nrt request in its context.
Jan
--
Siemens AG, T RDA IOT
Corporate Competence Center Embedded Linux
next prev parent reply other threads:[~2021-07-08 10:20 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-08 9:03 rt_task_shadow() secondary mode Richard Weinberger
2021-07-08 9:25 ` Jan Kiszka
2021-07-08 9:51 ` Richard Weinberger
2021-07-08 9:54 ` Jan Kiszka
2021-07-08 10:04 ` Richard Weinberger
2021-07-08 10:20 ` Jan Kiszka [this message]
2021-07-08 10:09 ` Philippe Gerum
2021-07-08 10:23 ` Jan Kiszka
2021-07-08 12:51 ` Philippe Gerum
2021-07-08 22:05 ` Richard Weinberger
2021-07-08 22:14 ` Richard Weinberger
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