PendSv not called or delayed call

[root]

Posted on February 28, 2014 at 17:23

Hello,

I have a strange issue using Atollic / JLink / STM32F2 working on a preemptive multitasking kernel. I initialize my interrupts priorities like this:

NVIC_SetPriorityGrouping(6); // there is only 2 levels of preemption, one for system, the other for interrupts. This gives 8 levels of sub-priority for interrupts. 
NVIC_SetPriority(SVCall_IRQn, 0x00); // set service call priority to highest priority 
NVIC_SetPriority(SysTick_IRQn, 0x7F); // set systick interrupt to low but preemptive 
NVIC_SetPriority(PendSV_IRQn, 0xFF); // set pend sv interrupt to low and not preemptive

And main function is called in thread mode (using PSP). In the SVC Handler, I check if a task switch if needed, then pend a PendSv interrupt like this:

SCB ->ICSR |= SCB_ICSR_PENDSVSET_Msk;

Debugging this with atollic, I have strange behavior, it seems the debugger skip interrupts when stepping (I have to place a breakpoint in the pendsv Handler to debug it), plus sometimes it is just not called at all. For what reason the PendSv interrupt could be delayed or disabled? I also tried to use the ITM_SendChar to send debug messages, but get hardfault trigger when using it ... except if I run it step by step using the debugger ....... Any idea ? Best regards, Thomas Legrand. #nvic

[root]

Posted on February 28, 2014 at 18:30

More info ...

After the SVC set the PENDSVSET bit and exits, the VECTPENDING shows 0xE, PRIMASK is 0, CONTROL is 3 (user mode), PENDSVSET is still set, VECTACTIVE is zero (no active interrupt).

Even ISRPREEMPT shows 1 (used in debug to show next instruction should be an interrupt).

But the PendSv Handler is not called ... I can continue debug, nothing changes, it should trigger the pendsv but doesn't .... what am I missing ?

Thomas.

[root]

Posted on February 28, 2014 at 18:31

More info ...

After the SVC set the PENDSVSET bit and exits, the VECTPENDING shows 0xE, PRIMASK is 0, CONTROL is 3 (user mode), PENDSVSET is still set, VECTACTIVE is zero (no active interrupt).

Even ISRPREEMPT shows 1 (used in debug to show next instruction should be an interrupt).

But the PendSv Handler is not called ... I can continue debug, nothing changes, it should trigger the pendsv but doesn't .... what am I missing ?

Thomas.

[jpeacock2399]

Posted on March 01, 2014 at 00:28

The STM32F2 series only has 4 levels for the NVIC.  Cortex M can go up to 8 but this is vendor dependent.  Try setting your NVIC priority group to 4 bits for the IRQ levels and skip the sub level preemption.

  Jack Peacock

[root]

Posted on March 03, 2014 at 11:14

Hello,

I need 2 levels of preemption (1 bit) and 8 levels of sub priority (3 bits).

Is my priority grouping wrong, should be 1 (the function is not well described, I inferred the parameter from code and datasheet, but I'm perhaps wrong) ?

The parameter of SetPriorityGrouping is the number of bits assigned to preemption levels ?

Thomas.