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Wake up tasks blocked on empty/full queue with error_status

Posted by ondrap-cze on January 7, 2016

Hi We are using FreeRTOS version 8.0.1 and our interest is about the blocked task on empty/full queue. We would like to have queue which can be closed. Function close will wake up all tasks blocked on empty/full queue with special error code (or exception) and all future requests for read or write to the queue will return this special error code (or exception). Same functionality is described in paper [1] on http://www.open-std.org/.

Is it possible to achieve this functionality with FreeRTOS queues or another synchronization primitives?

Our system uses tasks which receive shutdown signal and after received it terminates itself. But we started using queues for sending messages between tasks and this approach is not possible when task gets blocked on empty queue. Our primary concern is to implement proper shutdown procedure for every task.

Thanks, Ondrej

[1] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3533.html#closed_queues

Wake up tasks blocked on empty/full queue with error_status

Posted by rtel on January 7, 2016

There is an outstanding feature request, which is scheduled to be implemented "soon" (?) to allow tasks that are in the Blocked state to wait for an event to abort their wait, and re-enter the Ready state. That may simplify your particular scenario, but other than that, there is no way to close a queue. Perhaps you could implement this using a wrapper around the queue functions, or possibly even using the trace macros (although you may find trace macros are only in place after a read/write to a queue has already passed or failed).

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