82 lines
2.2 KiB
C
82 lines
2.2 KiB
C
#include <sys/types.h>
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#include <pthread.h>
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#include <stdio.h>
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/*
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* Child threads
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*/
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#define NTHREADS (4)
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#define STACK_SIZE (8 * 1024)
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#define LOCAL_COUNT (100000L)
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#define EXPECTED_GLOBAL_COUNT (LOCAL_COUNT * NTHREADS)
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struct thread_arg {
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int ti;
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long local_count;
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volatile long* global_count;
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pthread_mutex_t* mutex;
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};
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static void* thread_func(void* _arg) {
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struct thread_arg* arg = _arg;
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printf("Thread #%d: started\n", arg->ti);
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for (long i = 0; i < arg->local_count; i++) {
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pthread_mutex_lock(arg->mutex);
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(*arg->global_count)++;
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pthread_mutex_unlock(arg->mutex);
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}
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printf("Thread #%d: completed\n", arg->ti);
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return NULL;
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}
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int main(int argc, const char* argv[]) {
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/*
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* Multiple threads are to increase a global counter concurrently
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*/
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volatile long global_count = 0;
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pthread_t threads[NTHREADS];
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struct thread_arg thread_args[NTHREADS];
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/*
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* Protect the counter with a mutex
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*/
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pthread_mutex_t mutex;
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pthread_mutex_init(&mutex, NULL);
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/*
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* Start the threads
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*/
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for (int ti = 0; ti < NTHREADS; ti++) {
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struct thread_arg* thread_arg = &thread_args[ti];
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thread_arg->ti = ti;
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thread_arg->local_count = LOCAL_COUNT;
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thread_arg->global_count = &global_count;
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thread_arg->mutex = &mutex;
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if (pthread_create(&threads[ti], NULL, thread_func, thread_arg) < 0) {
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printf("ERROR: pthread_create failed (ti = %d)\n", ti);
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return -1;
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}
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}
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/*
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* Wait for the threads to finish
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*/
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for (int ti = 0; ti < NTHREADS; ti++) {
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if (pthread_join(threads[ti], NULL) < 0) {
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printf("ERROR: pthread_join failed (ti = %d)\n", ti);
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return -1;
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}
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}
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/*
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* Check the correctness of the concurrent counter
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*/
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if (global_count != EXPECTED_GLOBAL_COUNT) {
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printf("ERROR: incorrect global_count (actual = %ld, expected = %ld)\n",
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global_count, EXPECTED_GLOBAL_COUNT);
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return -1;
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}
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pthread_mutex_destroy(&mutex);
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return 0;
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}
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