STM4Cube+FreeRTOS: xTaskIncrementTick() could be called when pxCurrentTCB == NULL

dp65 · ‎2014-07-20

Posted on July 20, 2014 at 13:49

I’m running code, generated by STM32Cube and have dropped to HardFault_Handler() on start of execution.

By debugging I have found this issue:

STM32Cube code generator placed xPortSysTickHandler() into SysTick_Handler() for 1 ms tick counting.

xPortSysTickHandler() calls xTaskIncrementTick(), which execute follow code:

...

if( listCURRENT_LIST_LENGTH( &( pxReadyTasksLists[ pxCurrentTCB->uxPriority ] ) ) > ( UBaseType_t ) 1 )

...

But, clock system had initialized before any tasks have been created.

And interrupt SysTick_Handler() may occurs when no tasks and even scheduler is not running yet.

So, pointer pxCurrentTCB equal to zero at this moment and [pxCurrentTCB -> uxPriority] indicates some random value.

It caused system exception.

As temporary solution I just have added one of task creation procedure before clock initialization. That is not good coding, but works.

And... by the way, when latest version of FreeRTOS will be implemented into Cube?

stm32cube-t · ‎2014-07-21

Posted on July 21, 2014 at 13:47

Hello,

Can you please provide the .ioc of your STM32CubeMX project.

Thank you

stm32cube-t · ‎2014-07-21

Posted on July 21, 2014 at 15:29

This issue will be fixed in a next release. For now you will have to patch 'stm32fxxx_it.c' file manually as follows:

void

SysTick_Handler

(void)

{

if

(

xTaskGetSchedulerState

() !=

taskSCHEDULER_NOT_STARTED

)

{

xPortSysTickHandler

();

}

HAL_IncTick

();

}

dp65 · ‎2014-07-22

Posted on July 23, 2014 at 08:13

Thanks for answer!

Just for you information - replay fromReal Time Engineers ltd.:

The clock should not be initialised until the scheduler has started. The sequence used by FreeRTOS is as follows:

1) Ensure interrupts are disabled.

2) Configure clock to generate tick interrupts.

3) Start the first task (which automatically re-enables interrupts).

So the clock initialisation code must itself be enabling the systick, which it need not do as FreeRTOS will do that itself at the appropriate time.

One solution for you, which assumes the ST code is not also enabling interrupts, is to simply call taskENTER_CRITICAL (or globally disable interrupts) before the clock initialisation is done. The scheduler will automatically set the global interrupts and critical section state to be correct when it starts.

Regards!

D. Popov

PS: Please find requested .ioc in the attachment

________________

Attachments :

F4-Cube.ioc : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HzKA&d=%2Fa%2F0X0000000bLG%2F.5NBSf3xf_gHnyEgIctJPlyX1nWf6n1IZSqlLP3R0FE&asPdf=false

viacheslav · ‎2014-08-23

Posted on August 24, 2014 at 01:05

In this case you will not be able to run any initialization before FreeRTOS run. Also HAL_delay() will not work as expected because it depends on systick interrupt.