Mixing
Understanding Semaphore (Getting the wrong final value of 1)
0
I have made a semaphore initialized to 0. I start the program by creating three threads and then calling sema_func() where sema_wait() puts them in the waiting list. Now I make a 4th thread which wakes up one of the thread by calling sema_wake() function. However when all the threads wake up,shouldn't i get the final value of 0 instead of 1? Kindly guide me
My code:
#include <pthread.h>
#include <stdio.h>
#include <semaphore.h>
sem_t mySema;
void *sema_func(void *param) {
printf("SLEEPING THREAD %lu n", pthread_self());
sem_wait(&mySema);
printf("WOKE THREAD %lu n", pthread_self());
sleep(1);
sem_post(&mySema);
}
void *wake_func(void *param) {
int sema_value = 0;
sem_getvalue(&mySema, &sema_value);
printf("SEMA VALUE: %dn", sema_value);
sem_post(&mySema);
sleep(5);
sem_getvalue(&mySema, &sema_value);
printf("SEMA FINAL VALUE: %dn", sema_value);
}
int main(int argc, char *argv) {
sem_init(&mySema, 0, 0);
pthread_t t1; pthread_t t2; pthread_t t3; pthread_t t4;
pthread_create(&t1, NULL, sema_func, NULL);
pthread_create(&t2, NULL, sema_func, NULL);
pthread_create(&t3, NULL, sema_func, NULL);
sleep(4);
pthread_create(&t4, NULL, wake_func, NULL);
sleep(10);
}Output: -
pthreads
asked Nov 21 '18 at 10:58
Jawad ZaheerJawad Zaheer
245
add a comment |
0
I have made a semaphore initialized to 0. I start the program by creating three threads and then calling sema_func() where sema_wait() puts them in the waiting list. Now I make a 4th thread which wakes up one of the thread by calling sema_wake() function. However when all the threads wake up,shouldn't i get the final value of 0 instead of 1? Kindly guide me
My code:
#include <pthread.h>
#include <stdio.h>
#include <semaphore.h>
sem_t mySema;
void *sema_func(void *param) {
printf("SLEEPING THREAD %lu n", pthread_self());
sem_wait(&mySema);
printf("WOKE THREAD %lu n", pthread_self());
sleep(1);
sem_post(&mySema);
}
void *wake_func(void *param) {
int sema_value = 0;
sem_getvalue(&mySema, &sema_value);
printf("SEMA VALUE: %dn", sema_value);
sem_post(&mySema);
sleep(5);
sem_getvalue(&mySema, &sema_value);
printf("SEMA FINAL VALUE: %dn", sema_value);
}
int main(int argc, char *argv) {
sem_init(&mySema, 0, 0);
pthread_t t1; pthread_t t2; pthread_t t3; pthread_t t4;
pthread_create(&t1, NULL, sema_func, NULL);
pthread_create(&t2, NULL, sema_func, NULL);
pthread_create(&t3, NULL, sema_func, NULL);
sleep(4);
pthread_create(&t4, NULL, wake_func, NULL);
sleep(10);
}Output: -
pthreads
asked Nov 21 '18 at 10:58
Jawad ZaheerJawad Zaheer
245
add a comment |
0
0
0
I have made a semaphore initialized to 0. I start the program by creating three threads and then calling sema_func() where sema_wait() puts them in the waiting list. Now I make a 4th thread which wakes up one of the thread by calling sema_wake() function. However when all the threads wake up,shouldn't i get the final value of 0 instead of 1? Kindly guide me
My code:
#include <pthread.h>
#include <stdio.h>
#include <semaphore.h>
sem_t mySema;
void *sema_func(void *param) {
printf("SLEEPING THREAD %lu n", pthread_self());
sem_wait(&mySema);
printf("WOKE THREAD %lu n", pthread_self());
sleep(1);
sem_post(&mySema);
}
void *wake_func(void *param) {
int sema_value = 0;
sem_getvalue(&mySema, &sema_value);
printf("SEMA VALUE: %dn", sema_value);
sem_post(&mySema);
sleep(5);
sem_getvalue(&mySema, &sema_value);
printf("SEMA FINAL VALUE: %dn", sema_value);
}
int main(int argc, char *argv) {
sem_init(&mySema, 0, 0);
pthread_t t1; pthread_t t2; pthread_t t3; pthread_t t4;
pthread_create(&t1, NULL, sema_func, NULL);
pthread_create(&t2, NULL, sema_func, NULL);
pthread_create(&t3, NULL, sema_func, NULL);
sleep(4);
pthread_create(&t4, NULL, wake_func, NULL);
sleep(10);
}Output: -
pthreads
asked Nov 21 '18 at 10:58
Jawad ZaheerJawad Zaheer
245
I have made a semaphore initialized to 0. I start the program by creating three threads and then calling sema_func() where sema_wait() puts them in the waiting list. Now I make a 4th thread which wakes up one of the thread by calling sema_wake() function. However when all the threads wake up,shouldn't i get the final value of 0 instead of 1? Kindly guide me
My code:
#include <pthread.h>
#include <stdio.h>
#include <semaphore.h>
sem_t mySema;
void *sema_func(void *param) {
printf("SLEEPING THREAD %lu n", pthread_self());
sem_wait(&mySema);
printf("WOKE THREAD %lu n", pthread_self());
sleep(1);
sem_post(&mySema);
}
void *wake_func(void *param) {
int sema_value = 0;
sem_getvalue(&mySema, &sema_value);
printf("SEMA VALUE: %dn", sema_value);
sem_post(&mySema);
sleep(5);
sem_getvalue(&mySema, &sema_value);
printf("SEMA FINAL VALUE: %dn", sema_value);
}
int main(int argc, char *argv) {
sem_init(&mySema, 0, 0);
pthread_t t1; pthread_t t2; pthread_t t3; pthread_t t4;
pthread_create(&t1, NULL, sema_func, NULL);
pthread_create(&t2, NULL, sema_func, NULL);
pthread_create(&t3, NULL, sema_func, NULL);
sleep(4);
pthread_create(&t4, NULL, wake_func, NULL);
sleep(10);
}Output: -
#include <pthread.h>
#include <stdio.h>
#include <semaphore.h>
sem_t mySema;
void *sema_func(void *param) {
printf("SLEEPING THREAD %lu n", pthread_self());
sem_wait(&mySema);
printf("WOKE THREAD %lu n", pthread_self());
sleep(1);
sem_post(&mySema);
}
void *wake_func(void *param) {
int sema_value = 0;
sem_getvalue(&mySema, &sema_value);
printf("SEMA VALUE: %dn", sema_value);
sem_post(&mySema);
sleep(5);
sem_getvalue(&mySema, &sema_value);
printf("SEMA FINAL VALUE: %dn", sema_value);
}
int main(int argc, char *argv) {
sem_init(&mySema, 0, 0);
pthread_t t1; pthread_t t2; pthread_t t3; pthread_t t4;
pthread_create(&t1, NULL, sema_func, NULL);
pthread_create(&t2, NULL, sema_func, NULL);
pthread_create(&t3, NULL, sema_func, NULL);
sleep(4);
pthread_create(&t4, NULL, wake_func, NULL);
sleep(10);
}#include <pthread.h>
#include <stdio.h>
#include <semaphore.h>
sem_t mySema;
void *sema_func(void *param) {
printf("SLEEPING THREAD %lu n", pthread_self());
sem_wait(&mySema);
printf("WOKE THREAD %lu n", pthread_self());
sleep(1);
sem_post(&mySema);
}
void *wake_func(void *param) {
int sema_value = 0;
sem_getvalue(&mySema, &sema_value);
printf("SEMA VALUE: %dn", sema_value);
sem_post(&mySema);
sleep(5);
sem_getvalue(&mySema, &sema_value);
printf("SEMA FINAL VALUE: %dn", sema_value);
}
int main(int argc, char *argv) {
sem_init(&mySema, 0, 0);
pthread_t t1; pthread_t t2; pthread_t t3; pthread_t t4;
pthread_create(&t1, NULL, sema_func, NULL);
pthread_create(&t2, NULL, sema_func, NULL);
pthread_create(&t3, NULL, sema_func, NULL);
sleep(4);
pthread_create(&t4, NULL, wake_func, NULL);
sleep(10);
}pthreads
pthreads
asked Nov 21 '18 at 10:58
Jawad ZaheerJawad Zaheer
245
asked Nov 21 '18 at 10:58
Jawad ZaheerJawad Zaheer
245
asked Nov 21 '18 at 10:58
Jawad ZaheerJawad Zaheer
245
asked Nov 21 '18 at 10:58
Jawad ZaheerJawad Zaheer
245
asked Nov 21 '18 at 10:58
Jawad ZaheerJawad Zaheer
245
245
add a comment |
add a comment |
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