Re: [Xenomai-core] [BUG] racy xnshadow_harden under CONFIG_PREEMPT

[Jan Kiszka <jan.kiszka@domain.hid>]

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Dmitry Adamushko wrote:
>>> ...
> 
>> I have not checked it yet but my presupposition that something as easy as
>> :
>>> preempt_disable()
>>>
>>> wake_up_interruptible_sync();
>>> schedule();
>>>
>>> preempt_enable();
>> It's a no-go: "scheduling while atomic". One of my first attempts to
>> solve it.
> 
> 
> My fault. I meant the way preempt_schedule() and preempt_irq_schedule() call
> schedule() while being non-preemptible.
> To this end, ACTIVE_PREEMPT is set up.
> The use of preempt_enable/disable() here is wrong.
> 
> 
> The only way to enter schedule() without being preemptible is via
>> ACTIVE_PREEMPT. But the effect of that flag should be well-known now.
>> Kind of Gordian knot. :(
> 
> 
> Maybe I have missed something so just for my curiosity : what does prevent
> the use of PREEMPT_ACTIVE here?
> We don't have a "preempted while atomic" message here as it seems to be a
> legal way to call schedule() with that flag being set up.

When PREEMPT_ACTIVE is set, task gets /preempted/ but not removed from
the run queue - independent of its current status.

> 
> 
>>> could work... err.. and don't blame me if no, it's some one else who has
>>> written that nonsense :o)
>>>
>>> --
>>> Best regards,
>>> Dmitry Adamushko
>>>
>> Jan
>>
>>
>>
>>
> 
> 
> --
> Best regards,
> Dmitry Adamushko
> 
> 
> 
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> 
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