91 lines
1.6 KiB
C
91 lines
1.6 KiB
C
/*
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* sem_list1.c - Shows what can happen as a result of
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* uncontrolled access to a singly linked list
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <pthread.h>
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#include <semaphore.h>
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typedef struct node {
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int val;
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struct node* next;
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} node;
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typedef struct list {
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node* head;
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} list;
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// shared global
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static list mylist;
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// start flag
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volatile int start = 0;
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// The thread process
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void* thread_routine()
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{
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printf("Worker thread: %lu ready\n", pthread_self());
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// wait for start from master thread
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while(start == 0);
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for (int j = 0; j < 1000000; j++)
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{
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node* new_node = malloc(sizeof(node));
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new_node->val = j;
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new_node->next = mylist.head;
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mylist.head = new_node;
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}
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printf("Worker thread: %lu done\n", pthread_self());
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return NULL;
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}
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// Main process
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int main()
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{
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#define THREAD_COUNT 10
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pthread_t thr_ids[THREAD_COUNT];
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mylist.head = NULL;
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// Create the threads
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for(int i = 0; i < THREAD_COUNT; i++) {
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if(pthread_create(&thr_ids[i], NULL, thread_routine, NULL) == -1) {
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printf("COULD NOT CREATE A THREAD\n");
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exit(EXIT_FAILURE);
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}
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}
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// Signal threads to start
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start = 1;
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// Wait for all threads to finish
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for(int i = 0; i < THREAD_COUNT; i++) {
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pthread_join(thr_ids[i],NULL);
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}
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// Count the elements in the list
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int length = 0;
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node* itr = mylist.head;
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while(itr != NULL) {
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length++;
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itr = itr->next;
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}
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printf("List contains %d elements\n", length);
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// Free the list
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while(mylist.head != NULL) {
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node* to_delete = mylist.head;
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mylist.head = mylist.head->next;
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free(to_delete);
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}
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return EXIT_SUCCESS;
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}
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