Re: [Xenomai] __get_user/__put_user

[Jan Kiszka <jan.kiszka@web.de>]

On 2013-05-09 19:32, Gilles Chanteperdrix wrote:
> On 03/16/2013 09:50 PM, Gilles Chanteperdrix wrote:
> 
>> On 03/16/2013 09:28 PM, Jan Kiszka wrote:
>>
>>> On 2013-03-16 21:27, Gilles Chanteperdrix wrote:
>>>> On 03/16/2013 09:25 PM, Jan Kiszka wrote:
>>>>
>>>>> On 2013-03-16 21:19, Gilles Chanteperdrix wrote:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> xenomai asm-generic/syscall.h defines __xn_put_user/__xn_get_user as
>>>>>> aliases for __put_user/__get_user, which implementation, for the ARM
>>>>>> architecture calls might_fault() which triggers an ipipe_root_only() check.
>>>>>>
>>>>>> So, the question is, what is the best way of avoiding this issue? Remove
>>>>>> the call to might_fault() when compiling with CONFIG_IPIPE enabled?
>>>>>> Define __ipipe_safe_put_user which avoids the call to might_fault() ?
>>>>>
>>>>> Adjust might_fault() in a way that it only considers atomic non-root
>>>>> contexts as problematic.
>>>>
>>>>
>>>> atomic meaning with hardware irqs off? or within an irq handler? This
>>>> requires xenomai...
>>>
>>
>>> Hard irqs off || head domain stalled, I would say.
>>
>> ok, done, thanks.
>>
> 
> Actually, it does not work, the WARN_ON triggers in __rt_heap_bind for
> instance, which does some copies from user with hard irqs off.

Hmm, isn't that a real bug? The nucleus should then try to migrate to
Linux while the nklock is held - ouch...

Jan


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