[ros-dev] RE: [ros-diffs] [CVS reactos] fix broken work item impl.

[Alex Ionescu]

Hi,

I'm currently not able to look into this, but I'm afraid that you're 
both right and wrong.
Worker Threads/Queues are nothing more then an executive version of the 
kernel KQUEUE. I don't know why are using special structures and 
code...all that ExQueueWorkItem should do is call KeInsertQueue with the 
right parameters/queue name...I don't understand the point of using 
Events and Semaphores... KeRemoveQueue implements all the waiting 
necessary...a worker thread, in the entrypoint, simply loops by calling 
that function, which does the actual waiting (Even on ROS we have 
this!). You're both right that EVENTs and SEMAPHOREs are wrong...

I see it as utterly pointless to be working on a parallel implementation 
which seems to be broken no matter how you do it...just use KQUEUES like 
it should be done, and I believe this will be solved.

Best regards,
Alex Ionescu

Gunnar Dalsnes wrote:

>>you have changed the semaphore to a synchronisation event. If all worker
>>    
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>threads have a job and there are
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>>put more than one new job in the queue, only one of the jobs is delivered
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>to the workers. The first empty
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>>worker removes one job. The event is never signaled again. All other jobs
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>are never delivered to the
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>>workers. 
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>
>I don't understand how you are thinking. 
>
>SyncronizationEvent = AutoResetEvent. It shouldn't be possible for a work
>item not to be delivered. If any worker threads are allready running, the
>ExInterlockedRemoveHeadList loop will execute the work item. If any thread
>is waiting on the event, it will be woken. We/I could examine a more
>detailed scenario if you want.
>
>  
>
>>Compiling ros on ros isn't the real problem. I use three pc for testing.
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>On two pc I can compile
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>>ros on ros without any problems. The third pc is a smp machine. On my
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>third pc, the problem is somewhere in
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>>the smp code (and in many of my not commited changes).    
>>    
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>
>The new tcpip.sys generates lots of work items, and while compiling
>ros-on-ros it bsod'd for me with STATUS_SEMAPHORE_LIMIT_EXCEEDED exception.
>If you look at the old code, this can easily happend if the worker threads
>are busy looping and dequeing items, without ever entering the wait.
>
>
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