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Help with configASSERT in vPortExitCritical

Posted by booherbg on April 13, 2017

Hi all. I have an intermittant bug that I'm trying to track down. Essentially an assertion failure in line 413 of port.c -- basically the first line of vPortExitCritical():

~~~ void vPortExitCritical( void ) { configASSERT( uxCriticalNesting ); uxCriticalNesting--; if( uxCriticalNesting == 0 ) { portENABLE_INTERRUPTS(); } } ~~~

I am trying to get my debugger to get trapped here so I can see a call trace. Even with a trace I fear that the actual reason for the error would be a previous call to vPortExitCritical(), as the assertion is simply that uxCriticalNesting is actually 0.

I would love any tips on where to look for how to track this down. I suspect there may be an issue with priorities, or some rogue conditional branch that may be causing this. It feels like someone is calling vPortExitCritical() from outside a critical region (thus reducing uxCriticalNesting to 0 prematurely). Does that sound like a correct guess?

I'm running FreeRTOS 8.2.3 on an Arm Cortex M7, and a Segger J-LINK debugger.


Help with configASSERT in vPortExitCritical

Posted by rtel on April 13, 2017

You can add some code to give yourself a place to place a break point, as follows:

void vPortExitCritical( void )
     if( uxCriticalNesting == 0 )
         __asm volatile ( "NOP" );

     // Rest of vPortExitCritical() code goes here.

This uses GCC syntax. You can then place your breakpoint on the NOP instruction.

Help with configASSERT in vPortExitCritical

Posted by booherbg on April 13, 2017

Thank you. I'm giving this a try to see what my call trace looks like.

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