78 lines
1.5 KiB
C
78 lines
1.5 KiB
C
/*
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* mutex1.c - Uses a mutex lock to control access to a critical section
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* that increments two global variables
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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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// shared global
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static int counter1 = 0;
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static int counter2 = 0;
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// start flag
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volatile int start;
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// flag mutex
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pthread_mutex_t flag = PTHREAD_MUTEX_INITIALIZER;
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// The thread process
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void* thread_routine(void* args)
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{
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int me = *((int *) args);
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int you = me ? 0 : 1;
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printf("Worker thread: %d ready, you are %d\n",me,you);
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// wait for start from master thread
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while(!start);
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for (int j = 0; j < 1000000; j++)
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{
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pthread_mutex_lock(&flag);
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// this is the critical section
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counter1++;
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counter2++;
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// leaving critical section
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pthread_mutex_unlock(&flag);
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}
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printf("Worker thread: %d done\n",me);
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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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int val1 = 0;
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int val2 = 1;
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pthread_t thr1;
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pthread_t thr2;
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if(pthread_create(&thr1, NULL, thread_routine, (void*)&val1) == -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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if(pthread_create(&thr2, NULL, thread_routine, (void*)&val2) == -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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start = 1;
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pthread_join(thr1,NULL);
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pthread_join(thr2,NULL);
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printf("counter1: %d\n",counter1);
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printf("counter2: %d\n",counter2);
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pthread_mutex_destroy(&flag);
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return EXIT_SUCCESS;
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}
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