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Implementing a thread-safe printf function for multitasking environments

The following example demonstrates the implementation of the osPrintf function, a thread-safe equivalent to the standard C printf function. The osPrintf function is specifically designed to be accessed concurrently by multiple tasks within the system.

#include <stdio.h>
#include <stdarg.h>
#include "OS_API.h"


#define TASK_COUNT 8

HANDLE PrintMutexHandle;


void osPrintf(char *Message, ...)
{
  va_list ap;

  /* Wait for mutex */
  osWaitForObject(PrintMutexHandle, OS_INFINITE);

  /* Print string on the console or send it via RS-232 */
  va_start(ap, Message);
  vprintf(Message, ap);
  va_end(ap);

  /* Release mutex */
  osReleaseMutex(PrintMutexHandle);
}


ERROR WorkerTask(PVOID Arg)
{
  /* Mark parameter as unused */
  AR_UNUSED_PARAM(Arg);

  /* Print messages */
  while(1)
    osPrintf("Task %i prints message.\n", (int) Arg);
}


int main(void)
{
  int i;

  /* Initialization */
  arInit();
  stInit();
  osInit();

  /* Create mutex for printf function */
  PrintMutexHandle = osCreateMutex(NULL, FALSE);

  /* Create sender tasks */
  for(i = 0; i < TASK_COUNT; i++)
    osCreateTask(WorkerTask, (PVOID) (i + 1), 0, 0, FALSE);

  /* Start the operating system */
  osStart();

  /* Deinitialization */
  osDeinit();
  arDeinit();
  return 0;
}

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