Re: [Xenomai] [PATCH] Revert "ipipe: ipipe_request_irq(), ipipe_free_irq() are root-only services"

[Jan Kiszka <jan.kiszka@siemens.com>]

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?

>>  - in Xenomai 2.6 (at least, didn't check forge) as it calls with a
>>    hardened spin lock held into ipipe_virtualize_irq

This problem is something I vaguely recall we discussed before already
in the past. I think there was no good solution for the Xenomai 2
architecture.

In this light, let's remove those checks nevertheless.
Enabling/disabling the IRQ are separate calls, and those should be
instrumented as those cause the restriction.

> 
> Sorry, three bugs:
>  - in the RTDM spec as it always allowed rtdm_irq_request over RT task
>    contexts

Changing the spec and adding a runtime check will likely be no issue. No
sane driver should have made use of that option. I will file a patch.

Jan

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