We touched upon mutexes and what they are; now we are going to implement a C program that demonstrates how they work.
Create a new file called third_c_prog.c inside the c_programs directory.
vim third_c_prog.c
Add the following code to this file:
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
pthread_mutex_t mutex1 = PTHREAD_MUTEX_INITIALIZER;
pthread_t thread_id[4];
int counter = 0;
void *thread_processor()
{
pthread_mutex_lock( &mutex1 );
counter++;
printf(" Counter: %d\n",counter);
pthread_mutex_unlock( &mutex1 );
}
int main(void)
{
int i = 0;
int error;
while(i < 4) {
error = pthread_create(&(thread_id[i]), NULL, &thread_processor, NULL);
if (error != 0)
{
printf("\nthere was a problem creating thread: %s", strerror(error));
}
else
{
printf("\n Thread number %d created.\n", i);
}
pthread_join( thread_id[i], NULL);
i++;
}
}This program is a variation on the first...