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semaphore token counter is not limited

Thomas Rb

Hello,

µVision V5.12, CMSIS OS RTX V4.75

It seemed to me, that a binary Semaphore does not work correctly with my test code.
osSemaphoreWait returns a value of 4, but it is a binary semaphore.
Do I missunderstand something?

// compile without optimizations, level 0.

#include "cmsis_os.h"

osSemaphoreDef(sema);
osSemaphoreId sema;

int main (void) {
        int32_t tokens;

        sema = osSemaphoreCreate(osSemaphore(sema),1); /* create binary sema
                                         max count of tokens should be 1 */
        osSemaphoreRelease(sema); // try to increment sema
        osSemaphoreRelease(sema); // try to increment sema
        osSemaphoreRelease(sema); // try to increment sema

        tokens = osSemaphoreWait(sema,0); // the value of tokens is 4 after
        // execution, though I limited the sema counter to 1 token
            // is this a bug?
}

Thanks for reply

Thomas

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  • 0

    Hello Thomas,

    this is a problem of API versus implementation. From the API it seems that the parameter count specifies the maximum number of available resources. In the CMSIS-RTOS RTX implementation it is used as an initial resource count number. It is not remembered as the maximum number of available resources. Thus, every call to osSemaphoreRelease increases the number of available resources. We will fix this in a future release (in the API and the implementation).

    Kind regards,

    Christopher

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  • 0

    Hello Thomas,

    this is a problem of API versus implementation. From the API it seems that the parameter count specifies the maximum number of available resources. In the CMSIS-RTOS RTX implementation it is used as an initial resource count number. It is not remembered as the maximum number of available resources. Thus, every call to osSemaphoreRelease increases the number of available resources. We will fix this in a future release (in the API and the implementation).

    Kind regards,

    Christopher

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