[vbox-dev] Fix to #13802

[a.urakov at drweb.com]

Hi Klaus,

yes, I completely agree with you. Thanks again!

Regards,
Alexander

11.02.2015 20:04, Klaus Espenlaub пишет:
> Hi Alexander,
>
> this patch (after having to spend a LOT of time on analyzing the warped
> logic of the code) fixes a genuine issue. I haven't made up my mind if
> it's the best solution.
>
> The entire XPCOM code is rather convoluted, and an alternative solution
> would be that the thread which distributes work to the workers should be
> responsible for decreasing the free worker count *before* kicking the
> free workers. It doesn't matter which worker actually gets woken up.
> Unfortunately that's rather difficult to implement without a complete
> rewrite.
>
> Ultimately the true issue is the convoluted, hard to maintain code
> (maximizing the non-deterministic behavior and thus the mental effort to
> understand a small part of how the code works - the reason why this very
> evil and very rare bug survived).
>
> Redoing the code to be easier to understand is a huge effort, which
> makes me lean towards your solution.
>
> Klaus
>
> On 30.01.2015 15:56, a.urakov at drweb.com wrote:
>> Hello!
>>
>> We would like to contribute to VirtualBox under MIT license. We send our
>> changes to fix bug described at https://www.virtualbox.org/ticket/13802 .
>>
>> The idea is that we not only check waiting workers presence but also
>> compare amount of waiting workers and amount of requests. So when amount
>> of request is greater than amount of free workers (and situation not
>> changed after short sleeping) we create new worker. In this case there
>> will be always sufficient amount of workers.
>>
>> We find amount of requests by iterating through whole list and it seems
>> like it doesn't cause execution speed decreasing (due to not so big
>> requests queue). But if there will be some problems with it we can
>> correct code to count elements on every appending / removing operation
>> (this way not so good because count variable must be changed in every
>> append / remove / etc operation and every new operation in ipcList class).
>>
>> Regards,
>> Alexander
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