What could explain a HardFault when entering in critical region?

[Sebastien]

Hello,

We are developing an application which is using the app_scheduler (especially to put events etc.)

It seems that sometimes (very rarely) we detected a Hard Fault when the app_scheduler is calling the CRITICAL_REGION_ENTER() macro (into the app_scheduler.c). We have retrieved core registers when the panic appears:

• The program counter pointed to "sd_nvic_critical_region_enter" from sdk/import/s110_nrf51822/include/nrf_soc.h line 474 where we can find the supervisor call in order to disable irq.
• IPSR = 0x3 --> HardFault

Any ideas about what could induce this hard fault?

Thx!

[Susheel Nuguru]

Check if you are using APP_TIMER and if you have set RTC1 interrupt handler priority to APP_HIGH, then like RK said it will cause an hardfault in app_scheculer

below m_evt_schedule_func = app_timer_evt_schedule (set in APP_TIMER_INIT macro)

RTC1_IRQHandler->timer_timeouts_check()->timeout_handler_exec->m_evt_schedule_func->app_sched_event_put->CRITICAL_REGION_ENTER

[Susheel Nuguru]

good observation sebastien, there is a limitation on how you use CRITICAL_REGION_xx macro. You cannot use it when softdevice is disabled and have the macro SOFTDEVICE_PRESENT defined in your project. you can just use below when you are not using softdevice

static uint32_t m_in_critical_region = 0;

void critical_region_enter(void)
{
    __disable_irq();    
    m_in_critical_region++;    
}

void critical_region_exit(void)
{
    m_in_critical_region--;    
    if (m_in_critical_region == 0)
    {
        __enable_irq();
    }
}

This code is also available in components\libraries\util\app_util_platform.c