[asterisk-dev] [Code Review] Add a serializer interface to the threadpool

[Mark Michelson]

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/trunk/main/taskprocessor.c
<https://reviewboard.asterisk.org/r/2323/#comment14842>

    This change is a bit troublesome. One of the reasons that tps_taskprocessor_pop() can return NULL is if the taskprocessor is shutting down. A common idiom in use is to loop calling ast_taskprocessor_execute() until it returns 0. Now if someone decides to shut down a taskprocessor that still has tasks in it, then the code that is looping over ast_taskprocessor_execute will not break out of its loop since ast_taskprocessor_execute will continually return non-zero.
    
    I think that if tps_taskprocessor_pop() returns NULL, we should unconditionally return 0 because either
    1) There were no tasks to pop off
    2) The taskprocessor has shut down and so we shouldn't be attempting to execute any more. 



/trunk/main/threadpool.c
<https://reviewboard.asterisk.org/r/2323/#comment14843>

    You should increase the refcount of pool when you set ser->pool. This way if someone were to shut down the threadpool before unreffing the serializer, they wouldn't run into trouble.
    
    Naturually this would mean decreasing the refcount in serializer_dtor()



/trunk/tests/test_threadpool.c
<https://reviewboard.asterisk.org/r/2323/#comment14844>

    "highlanger?" Did you mean "highlander?"


- Mark


On Feb. 8, 2013, 3:24 p.m., David Lee wrote:
> 
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> (Updated Feb. 8, 2013, 3:24 p.m.)
> 
> 
> Review request for Asterisk Developers and Mark Michelson.
> 
> 
> Summary
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> 
> This patch adds the ability to create a serializer from a thread pool. A
> serializer is a ast_taskprocessor with the same contract as a default
> taskprocessor (tasks execute serially) except instead of executing out
> of a dedicated thread, execution occurs in a thread from a
> ast_threadpool. Think of it as a lightweight thread.
> 
> While it guarantees that each task will complete before executing the
> next, there is no guarantee as to which thread from the pool individual
> tasks will execute. This normally only matters if your code relys on
> thread specific information, such as thread locals.
> 
> This patch also fixes a bug in how the 'was_empty' parameter is computed
> for the push callback.
> 
> 
> Diffs
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> 
>   /trunk/include/asterisk/threadpool.h 381085 
>   /trunk/main/taskprocessor.c 381085 
>   /trunk/main/threadpool.c 381085 
>   /trunk/tests/test_threadpool.c 381085 
> 
> Diff: https://reviewboard.asterisk.org/r/2323/diff
> 
> 
> Testing
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> 
> Unit testing.
> 
> 
> Thanks,
> 
> David
> 
>

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