SB-21: Salvo: Task Problems with AVR-GCC

[Salvo Tech Support]

Applies To

All Salvo for Atmel AVR and MegaAVR users who are using the AVR-GCC compiler.

Description of Problem

The runtime behavior of a task is not what is expected. For example, the <flag> variable in this task will not be set to the proper value:

code:

---

void TaskCount( void )
{
  static unsigned int flag;
  for (;;) 
  {
    counter++;
    if ((counter % 2) == 0) 
    {
      OS_Yield(TaskCount99);
      flag = 0; 
    }
  }
}

---

The problem is due to a register allocation / filling optimization that the AVR-GCC compiler is applying to the task. This optimization is incompatible with Salvo's task structure due to the fact that Salvo tasks can be (re-)entered after every context switch.

Suggested Workaround

Replace OS_Yield() in salvoincportgccavr.h with:

code:

---

#define OS_Yield(label) do { OSCtxSw(); __asm__ __volatile__(" nop"::); } while (0)

---

Fixed In

v3.2.4

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