TaskQueue : double conditional-sequence execution (C++)

Question

I'm writing a server application, task oriented. Each Session (client) send packets to the server, the server enqueues them as Tasks, and workers (threads) handle them. Constraints are :

Tasks from a same Session have to be always sequentially executed ( => if a thread begin to handle a Task of a Session, another thread cannot handle a Task for the same Session while the first is not finished)
Tasks of some types have to be sequentially executed
Tasks of some other type don't have to be sequentially executed

What could be the best approach to do that ? how do we call this concept ? (I guess it is not double conditional-sequence execution)

I ideally would use TBB to achieve that but I don't know if a feature of TBB just fit for my need. (I'm open for any other propositions)

Here a piece of "pseudo-code" which would be my first idea [EDIT: but is wrong, sequential execution is not assured, but the code could explain my idea] :

struct Session {
    atomic<bool> locked;
}
struct Task {
    char type;
    Session* session;
    void execute() { ; }
};

atomic<bool> type_locked[SEQ_TYPE_NUMBER];

threadsafe_selfiterable_list<Task> list;

void do() {
    while( alive ) 
    {
        if( list.empty() )
            relax();
        if( list.has_next() ) {
            task = list.next();
            if( !compare_and_swap( task.session->locked, true ) ) {
                if( is_non_sequential_task_type( task.type ) ) {
                    queue.pop();
                    task.execute();
                } else if( !compare_and_swap( type_locked[task.type], true ) ) {
                    queue.pop();
                    task.execute();
                    type_locked[task.type] = false;
                }
                task.session->locked = false;
            }
        } else 
            list.rewind();
    }
}

score 0 · Answer 1 · answered Jul 23 '13 at 13:54

0

Define a 'TaskCollection' Task that can hold, and execute, other tasks. If there are sequential task/s, shove them into a TaskCollection and submit that to your threadpool.

answered Jul 23 '13 at 13:54

Martin James

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The problem is the "double" sequential : a same task is sequential by his 'producer', and can be by the type. (note that my pseudo-code is currently wrong) – Malandrain Jul 23 '13 at 14:00

TaskQueue : double conditional-sequence execution (C++)

1 Answers1