51 lines
1.1 KiB
C
51 lines
1.1 KiB
C
/*
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* pthreads_race_atomic.c - Uses an atomic add instruction to prevent
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* the race condition that can happen when
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* multiple threads modify a global value at the
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* same time.
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*/
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#include <pthread.h>
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#include <stdatomic.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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atomic_int global_value = 0;
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void *thread_routine()
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{
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for (int i = 0; i < 1000000; i++)
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{
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atomic_fetch_add(&global_value, 1);
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}
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return NULL;
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}
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int main()
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{
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// Create 5 threads
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pthread_t thr_id[5];
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for (int i = 0; i < 5; i++)
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{
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if (pthread_create(&thr_id[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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// Wait for all threads to finish
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for (int i = 0; i < 5; i++)
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{
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pthread_join(thr_id[i], NULL);
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}
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// Print out final value of global value
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// 5 threads * 100000000 iterations - expected value is 500000000
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printf("PARENT READS GLOBAL: %d\n", global_value);
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// Return success
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return 0;
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}
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