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sem_counter.c
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sem_counter.c
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/types.h>
#include <time.h>
#define PATH "/mnt/d/homework/thread-saft-counter/key"
union semun
{
int val;
struct semid_ds* buf;
ushort* array;
};
typedef struct __counter_t
{
key_t key;
int value;
int semid;
union semun arg;
} counter_t;
unsigned int loop_cnt;
counter_t counter;
int init(counter_t* c)
{
c->key = ftok(PATH, 'z');
c->value = 0;
c->semid = semget(c->key, 1, 0600 | IPC_CREAT);
c->arg.val = 1;
semctl(c->semid, 0, SETVAL, c->arg);
}
void increment(counter_t* c)
{
struct sembuf s;
s.sem_num = 0;
s.sem_op = -1;
s.sem_flg = 0;
semop(c->semid, &s, 1);
c->value++;
s.sem_num = 0;
s.sem_op = 1;
s.sem_flg = 0;
semop(c->semid, &s, 1);
}
void decrement(counter_t* c)
{
struct sembuf s;
s.sem_num = 0;
s.sem_op = -1;
s.sem_flg = 0;
semop(c->semid, &s, 1);
c->value--;
s.sem_num = 0;
s.sem_op = 1;
s.sem_flg = 0;
semop(c->semid, &s, 1);
}
int get(counter_t* c)
{
struct sembuf s;
s.sem_num = 0;
s.sem_op = -1;
s.sem_flg = 0;
semop(c->semid, &s, 1);
int rc = c->value;
s.sem_num = 0;
s.sem_op = 1;
s.sem_flg = 0;
semop(c->semid, &s, 1);
return rc;
}
void* mythread(void* arg)
{
char* letter = arg;
int a;
printf("%s: begin\n", letter);
for (a = 0; a < loop_cnt; a++)
{
increment(&counter);
}
printf("%s: done\n", letter);
return NULL;
}
int main(int argc, char* argv[])
{
clock_t start, end;
float result;
loop_cnt = atoi(argv[1]);
init(&counter);
printf("semid=%d\n", counter.semid);
start = clock(); /*시간 측정 시작*/
pthread_t p1, p2;
printf("main: begin [counter = %d]\n", get(&counter));
pthread_create(&p1, NULL, mythread, "A");
pthread_create(&p2, NULL, mythread, "B");
pthread_join(p1, NULL);
pthread_join(p2, NULL);
end=clock(); /*시간 측정 종료*/
result = (float)(end-start)/CLOCKS_PER_SEC;
printf("main: done [counter: %d] [should be: %d]\n", get(&counter), loop_cnt * 2);
printf("소요시간 : %.3f\n", result);
return 0;
}