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A synchronization barrier

Posted by Martin Velek on August 24, 2009

how is the simplest implementation of barrier in FreeRTOS? I mean situation when a task is waiting for two or more events to continue. Having two or more semaphores/mutexes is not memory effective(some post notes that for one semaphore a 100 byte is requested).
I think that vSemaphoreCreateCounting() cannot be used for this purpose because a task is waken if the value is != 0.

Thank you for your advice.

If it is not possible I would suggest this feature.
xSemaphoreCreateBarrier( unsigned portBASE_TYPE uxMaxCount, unsigned portBASE_TYPE uxInitialCount). If a this type of semaphore is taken, the task will wait until uxInitialCount == uxMaxCount.

RE: A synchronization barrier

Posted by sotd on August 24, 2009
How about define integer to hold bit flags, one event for a bit, then use semaphore to block. When task unblock check integer to see if events happened and if no block again. ?

RE: A synchronization barrier

Posted by Martin Velek on August 25, 2009
Thank you vm. It seems to be working but I would rather use "n" integers, every for one event to avoid protecting bit flag itself or entering critical section. E.g. for n = 2, while(a == 0 || b==0) {semTake()}.

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