A Program to Test Deadlock

In the following program, we will try to test a deadlock scenario.

In this scenario, we are creating two threads, MY_THREAD_1 and MY_THREAD_2 . Moreover, we have two resources, resourceA and resourceB .

Source code of deadlock.c

#include <pthread.h> #include <stdio.h> #include <sched.h> #include <time.h> #define NUM_OF_THREADS 2 #define MY_THREAD_1 1 #define MY_THREAD_2 2 pthread_t threads[NUM_OF_THREADS]; struct sched_param nrt_param; pthread_mutex_t resourceA, resourceB; volatile int resourceACount=0, resourceBCount=0, noWait=0; void *grabresources(void *threadid) { if((int)threadid == MY_THREAD_1) { printf("Thread-1 is grabbing resources...\n"); pthread_mutex_lock(&resourceA); resourceACount++; if(!noWait) sleep(1000000); printf("Thread-1 has received resource-A, trying for resource-B...\n"); pthread_mutex_lock(&resourceB); resourceBCount++; printf("Thread-1 has received resource-A and resource-B...\n"); pthread_mutex_unlock(&resourceB); pthread_mutex_unlock(&resourceA); printf("Thread-1 is complete...\n"); } else { printf("Thread-2 is grabbing resources...\n"); pthread_mutex_lock(&resourceB); resourceBCount++; if(!noWait) usleep(1000000); printf("Thread-2 has received resource-B, trying for resource-A...\n"); pthread_mutex_lock(&resourceA); resourceACount++; printf("Thread-2 has received resource-B and resource-A...\n"); pthread_mutex_unlock(&resourceA); pthread_mutex_unlock(&resourceB); printf("Thread-2 is complete...\n"); } pthread_exit(NULL); } int main (int argc, char *argv[]) { int status, safe=0; resourceACount=0, resourceBCount=0, noWait=0; if(argc < 2) { printf("Will set up unsafe deadlock scenario...\n"); } else if(argc == 2) { if(strncmp("safe", argv[1], 4) == 0) safe=1; else if(strncmp("race", argv[1], 4) == 0) noWait=1; else printf("Will set up unsafe deadlock scenario...\n"); } else { printf("Usage: deadlock [safe|race|unsafe]\n"); } pthread_mutex_init(&resourceA, NULL); pthread_mutex_init(&resourceB, NULL); printf("Creating thread %d\n", MY_THREAD_1); status = pthread_create(&threads[0], NULL, grabresources, (void *)MY_THREAD_1); if (rc) { printf("ERROR: pthread_create() status is %d\n", status); perror(NULL); exit(-1); } printf("Thread-1 spawned\n"); if(safe) { if(pthread_join(threads[0], NULL) == 0) printf("Thread-1: %d done\n", threads[0]); else perror("Thread-1"); } printf("Creating thread %d\n", MY_THREAD_2); status = pthread_create(&threads[1], NULL, grabresources, (void *)MY_THREAD_2); if (rc) { printf("ERROR: pthread_create() status is %d\n", status); perror(NULL); exit(-1); } printf("Thread-2 spawned\n"); printf("resourceACount=%d, resourceBCount=%d\n", resourceACount, resourceBCount); printf("will try to join CS threads unless they deadlock\n"); if(!safe) { if(pthread_join(threads[0], NULL) == 0) printf("Thread-1: %d done\n", threads[0]); else perror("Thread-1"); } if(pthread_join(threads[1], NULL) == 0) printf("Thread-2: %d done\n", threads[1]); else perror("Thread-2"); if(pthread_mutex_destroy(&resourceA) != 0) perror("mutex A destroy"); if(pthread_mutex_destroy(&resourceB) != 0) perror("mutex B destroy"); printf("Everyting is complete...\n"); exit(0); }

To compile the Program use

$gcc deadlock.c -o deadlock -lpthread

To run

$./deadlock

Happy Exploring!