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Date: Thu, 20 Sep 2012 15:01:36 +0200
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai] [PATCH] Revert "ipipe: ipipe_request_irq(),
 ipipe_free_irq() are root-only services"
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To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: "Mauerer, Wolfgang" <wolfgang.mauerer@siemens.com>, Xenomai <xenomai@xenomai.org>

On 09/20/2012 01:15 PM, Jan Kiszka wrote:

> On 2012-09-20 12:57, Jan Kiszka wrote:
>> On 2012-09-20 12:56, Jan Kiszka wrote:
>>> On 2012-09-20 12:49, Philippe Gerum wrote:
>>>> On 09/20/2012 12:37 PM, Jan Kiszka wrote:
>>>>> This reverts commit 073ff1e8045d0311b8cf390687c0ba3619681672.
>>>>>
>>>>> Both service are NOT just root-only services. E.g., rtdm_irq_request
>>>>> requires by specification support also over non-Linux contexts.
>>>>
>>>> Nack. We can't run the enable code for MSIs over non-root, and
>>>> that code typically follows the irq request. Besides, we want to mask
>>>> the source upon irq free to handle the SMP case properly, which we could
>>>> not do from non-root with MSIs.
>>>>
>>>> So either we have both request+enable and free usable over non-root, or
>>>> there is no point.
>>>
>>> OK, I get the point with legacy MSI. Then we have two other bugs to solve:
>>>  - in I-pipe as it holds a hardened spin lock across enable/disable (of
>>>    MSIs)
> 
> I think this bug may only manifest over ARM as that arch does
> enable/disable_irq() inside __ipipe_enable/disable_irqdesc - unless
> something prevents that enabling will ever happen for interrupts that
> need Linux locks to work. Is that assured?


ARM does that because otherwise interrupts are not enabled after a call
to eg. rtdm_irq_request, and calling rtdm_irq_enable does not work,
calling request_irq is required to get them working.

-- 
                                                                Gilles.