vSemaphoreCreateBinary

Kernel
1

anonymous wrote on Wednesday, November 13, 2013:

I have two Binary semaphores its not working simultaneously
here if i comment vReadtask vCriticalTask will execute and if comment vCriticalTask , vReadtask will execute i cant use both simultaneously. What could be the reason? please help

vSemaphoreCreateBinary( xBinarySemaphore );
vSemaphoreCreateBinary( xReadSemaphore );

and two tasks

xTaskCreate( vReadTask, “Handler”, MEDIUM_STACK_SIZE, NULL, 11, &xReadHandler);
xTaskCreate(vCriticalTask,“Critical”, MEDIUM_STACK_SIZE,NULL,12,&xCriticalHandle);

void vReadTask( void *pvParameters )
{
for( ;; )
{
xSemaphoreTake( xReadSemaphore, portMAX_DELAY );

     //read code
}

}

void vCriticalTask( void *pvParameters )
{
for( ;; )
{
xSemaphoreTake( xBinarySemaphore, portMAX_DELAY );
//critical code
}
}

2

richard_damon wrote on Wednesday, November 13, 2013:

Not seeing the SemaphoreGive code, the only problems that I can see is you might be running out of heap.

What exactly do you comment out to make one side to work.

3

anonymous wrote on Wednesday, November 13, 2013:

I have many tasks in my program all others are work fine. The problem is in these two tasks, i can use either one of this task SemaphoreGive() using some other tasks, i comment the create task
////xTaskCreate( vReadTask, “Handler”, MEDIUM_STACK_SIZE, NULL, 11, &xReadHandler);

xTaskCreate(vCriticalTask,“Critical”, MEDIUM_STACK_SIZE,NULL,12,&xCriticalHandle);

this time CriticalTask will work

xTaskCreate( vReadTask, “Handler”, MEDIUM_STACK_SIZE, NULL, 11, &xReadHandler);

///xTaskCreate(vCriticalTask,“Critical”,MEDIUM_STACK_SIZE,NULL,12,&xCriticalHandle;

this time ReadTask will work.

4

anonymous wrote on Wednesday, November 13, 2013:

Yes, the error was in my configTOTAL_HEAP_SIZE i increased heap size problem solved. Thank you so much :slight_smile:

5

anonymous wrote on Wednesday, November 13, 2013:

void vReadTask( void *pvParameters )
{
for( ;; )
{
xSemaphoreTake( xReadSemaphore, portMAX_DELAY );
//read code
}
}

Here the read code will execute first time (program starting) before giving a semaphore. why this happening? how to avoid this?

6

davedoors wrote on Wednesday, November 13, 2013:

Look at the vSemaphoreCreateBinary() definition in semphr.h. You will see it is given after it is created so the first take will pass. If you don’t want that then take the semaphore straight after you have created it, before you use it in your task.

7

rtel wrote on Wednesday, November 13, 2013:

The head revision in SVN currently has a new xSemaphoreCreateBinary() function that works like all the other semaphore create function (a function that returns the semaphore) so the vSemaphoreCreateBinary() macro (note with a ‘v’ prefix) can be retired - although it will remain in the source code for backward compatibility. The ‘x’ version creates an empty semaphore, so a ‘give’ must be performed before a ‘take’ will pass.

Regards.