108 lines
2.0 KiB
C
108 lines
2.0 KiB
C
s /*
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* sem_list2.c - Uses a semaphore as a way to control access
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* to a critical section for a singly linked list
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*/
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#include <pthread.h>
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#include <semaphore.h>
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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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typedef struct node
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{
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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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{
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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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// flag semaphore
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sem_t flag;
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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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;
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for (int j = 0; j < 1000000; j++)
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{
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sem_wait(&flag);
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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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sem_post(&flag);
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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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sem_init(&flag, 0, 1);
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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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{
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if (pthread_create(&thr_ids[i], NULL, thread_routine, NULL) == -1)
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{
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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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{
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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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{
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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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{
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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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sem_destroy(&flag);
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return EXIT_SUCCESS;
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}
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