Simple multithread (main+2 threads) code raising out of memory error

Mbed OS
1

I am trying to create two threads in addition to main just to see how it works. If I create only one and control the last variable from the button callback, program works. If I create two, like below, I get Operator new out of memory error directly at the start. What is the reason for this ? The board is NUCLEO F072RB.

#include "mbed.h"

DigitalOut led1(LED1);
InterruptIn button1(BUTTON1);

Thread thread1;
Thread thread2;

uint32_t last;

void fThread1() {

  printf("T1\n");

  while (true) {

    led1 = !led1;
    if (last == 1) {
      ThisThread::sleep_for(100ms);
    } else {
      ThisThread::sleep_for(500ms);
    }

  }

}

void fThread2() {

  printf("T2\n");

  while (true) {

    ThisThread::flags_wait_any(0x01);
    printf("change\n");
    last = (last == 1) ? 2 : 1;

  }

}

void fButton() {
  thread2.flags_set(0x01);
  //last = (last == 1) ? 2 : 1;
} 

int main()
{

  printf("S\n");

  last = 1;

  thread1.start(callback(fThread1));
  thread2.start(callback(fThread2));

  button1.mode(PullNone);
  button1.rise(callback(fButton));

  printf("L\n");

  while (true);

  return 0;

}
2

Ahoj,

that is problem of resources maybe? Your board have only 16KB of SRAM and the full MbedOS functionally need a lot of resources.

The bare metal profile (no RTOS functionality) is optimal for this memory size with Mbed.

BR, Jan

3

I think thats true, the default stacksize is 4 k, in total 12 k for main + 2 threads.
The thread constructor has overloads where a reduced stacksize can be supplied, but with 16 k its not fun.
Bare Metal and events maybe a better solution.

4

I need to pay attention to numbers more :slight_smile: Thanks @JohnnyK

5

Thanks @JojoS, I will try reducing the stack size just for the sake of trying but then try bare metal profile or another board.

6

Just to confirm, the issue is definitely due to resources. I tried the same code on a different board (256K ram) and it works with no issues.

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