Re: [uml-devel] IRQ handler reentrancy

[Anton Ivanov <anton.ivanov@kot-begemot.co.uk>]

Patch in your queue, current code looks OK.

I will try to assemble the full ubd acceleration sequence of patches 
this afternoon to submit that as well.

A.

On 11/12/15 18:38, Richard Weinberger wrote:
> Am 11.12.2015 um 12:24 schrieb Anton Ivanov:
>> On 11/12/15 08:16, Richard Weinberger wrote:
>>> Am 11.12.2015 um 07:58 schrieb Anton Ivanov:
>>>>>> 2. I cannot catch what is wrong with the current code in signal.c. When
>>>>>> I read it, it should not produce re-entrancy. But it does.
>>>>> Sorry for the delay. Until now I did not find the time to dig into that.
>>>>> Did you find the offending code in signal.c?
>>>> Yes.
>>>>
>>>> Unblock signals is logically incorrect - it will re-trigger an
>>>> interrupts even if there is an interrupt in flight whose processing has
>>>> not been finished.
>>>>
>>>> I tried several approaches both with the original poll() controller and
>>>> with my epoll() based version, some show promise.
>>>>
>>>> I had to put it aside until next Friday as I have some stuff due at work
>>>> so I cannot spare time to work on it until then. Once I get that out of
>>>> the way I should be able to spare it a day or two which should be enough
>>>> to finish it.
>>>>
>>>> Ditto for the UBD improvements.
>>> One thing we have to consider is that's legit to have SIGIO nested.
>> Correct. That is considered :)
>>
>> Both when looking at poll() and epoll()
>>
>> However, it is not legit to have sigio on a specific fd nested. That is mostly safe for the poll() version, but will need to be accounted for in any surgery on the irq controller.
> So, the current code is fine unless you switch to epoll()?
> Is it because you use epoll() in edge-triggered mode?
>
> Thanks,
> //richard
>


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