deadlock example

deadlock.c

#include <stdio.h>
#include <pthread/pthread.h>
void* someprocess(void* arg);
void *anotherprocess(void* arg);

pthread_mutex_t lock;
pthread_t tid[2];
int counter;
int main(int argc, const char * argv[]) {
    if (pthread_mutex_init(&lock, NULL) != 0) {
        printf("\n mutex init has failed\n");
        return 1;
    }
    // insert code here...
    pthread_create(&(tid[0]),
                   NULL,
                   &someprocess, NULL);
    pthread_create(&(tid[1]),
                   NULL,
                   &someprocess, NULL);
    pthread_join(tid[1], NULL);
    pthread_join(tid[0], NULL);
    pthread_mutex_destroy(&lock);
    return 0;
}

void *someprocess(void* arg){
    pthread_mutex_lock(&lock);
    //try to gather lock again results deadlock.
    pthread_mutex_lock(&lock);

    unsigned long i = 0;
    counter += 1;
    printf("\n Job %d has started\n", counter);
    for (i = 0; i < (0xFFFFFFFF); i++)
        ;
    printf("\n Job %d has finished\n", counter);

    pthread_mutex_unlock(&lock);
    return NULL;
}

pthread_rcrsv.c

#include <stdio.h>
#include <pthread.h>

pthread_mutex_t recursive_mutex;
int avar;
void recursive_function(int n) {
    pthread_mutex_lock(&recursive_mutex);

    if (n > 0) {
        avar = n;
        printf("Entering recursive_function with n = %d , avar = %d\n", n, avar);
        recursive_function(n - 1);
    }

    printf("Exiting recursive_function with n = %d, avar = %d\n", n, avar);

    pthread_mutex_unlock(&recursive_mutex);
}

int main() {
    pthread_mutexattr_t mutex_attr;
    pthread_mutexattr_init(&mutex_attr);
    pthread_mutexattr_settype(&mutex_attr, PTHREAD_MUTEX_RECURSIVE);

    pthread_mutex_init(&recursive_mutex, &mutex_attr);

    recursive_function(3);

    pthread_mutex_destroy(&recursive_mutex);
    pthread_mutexattr_destroy(&mutex_attr);

    return 0;
}