How to coordonate threads in C
0
I have a little issue and I don't understand why my code doesn't work.
The purpose of the code is to use 3 different threads to display the sequence:
(abc)*
The output shows only one 'A' ...
sem_t mutex;
char turn = 'a';
void displayA()
{
for(int i = 0; i < 100; i++)
{
sem_wait(&mutex);
if (turn == 'a')
{
printf("A");
turn = "b";
printf("%c", turn);
}
sem_post(&mutex);
}
return NULL;
}
int main()
{
sem_init(&mutex, 0, 1);
pthread_t thread1_id;
pthread_t thread2_id;
pthread_t thread3_id;
pthread_create(&thread1_id, NULL, displayA, NULL);
pthread_create(&thread2_id, NULL, displayB, NULL);
pthread_create(&thread3_id, NULL, displayC, NULL);
pthread_join(thread1_id, NULL);
pthread_join(thread2_id, NULL);
pthread_join(thread3_id, NULL);
//sem_destroy(&mutex);
printf("n END mainn");
return 0;
}
Thanks you for any help
c multithreading pthreads mutex semaphore
asked Nov 18 '18 at 17:45
John DoeJohn Doe
386
|
show 4 more comments
0
I have a little issue and I don't understand why my code doesn't work.
The purpose of the code is to use 3 different threads to display the sequence:
(abc)*
The output shows only one 'A' ...
sem_t mutex;
char turn = 'a';
void displayA()
{
for(int i = 0; i < 100; i++)
{
sem_wait(&mutex);
if (turn == 'a')
{
printf("A");
turn = "b";
printf("%c", turn);
}
sem_post(&mutex);
}
return NULL;
}
int main()
{
sem_init(&mutex, 0, 1);
pthread_t thread1_id;
pthread_t thread2_id;
pthread_t thread3_id;
pthread_create(&thread1_id, NULL, displayA, NULL);
pthread_create(&thread2_id, NULL, displayB, NULL);
pthread_create(&thread3_id, NULL, displayC, NULL);
pthread_join(thread1_id, NULL);
pthread_join(thread2_id, NULL);
pthread_join(thread3_id, NULL);
//sem_destroy(&mutex);
printf("n END mainn");
return 0;
}
Thanks you for any help
c multithreading pthreads mutex semaphore
asked Nov 18 '18 at 17:45
John DoeJohn Doe
386
1
Do you want to associate each character to one thread or you just want a thread to print a letter? If it's the second one you just need a simple lock and a character that represents what to print. You acquire the lock, see what you need to print, release the lock. You can also do it (easily) with semaphores. You must also implement the logic to print all other characters in your sequence
– simo-r
Nov 18 '18 at 17:58
1
The code you posted would not compile because it is missingdisplayBanddisplayC. Also,turn = "b"will be flagged. Please post your full code that compiles and links cleanly
– Craig Estey
Nov 18 '18 at 18:10
I couldn't post all my code because it was too long, but the functions displayB and displayC exist:
– John Doe
Nov 18 '18 at 19:13
1
@JohnDoe Posting code that does not compile cleanly is a red flag, indicating to the reader that you are already misinterpreting what you think you're seeing. Post a Minimal, Complete, and Verifiable example. The stackoverflow interface should allow you to post your minimal example program.
– Gil Hamilton
Nov 18 '18 at 22:13
The posted code does not compile! Amongst other things, it is missing the#includestatements needed for the needed header files. Are you expecting us to guess as to which header files are needed?
– user3629249
Nov 18 '18 at 23:22
|
show 4 more comments
0
0
0
I have a little issue and I don't understand why my code doesn't work.
The purpose of the code is to use 3 different threads to display the sequence:
(abc)*
The output shows only one 'A' ...
sem_t mutex;
char turn = 'a';
void displayA()
{
for(int i = 0; i < 100; i++)
{
sem_wait(&mutex);
if (turn == 'a')
{
printf("A");
turn = "b";
printf("%c", turn);
}
sem_post(&mutex);
}
return NULL;
}
int main()
{
sem_init(&mutex, 0, 1);
pthread_t thread1_id;
pthread_t thread2_id;
pthread_t thread3_id;
pthread_create(&thread1_id, NULL, displayA, NULL);
pthread_create(&thread2_id, NULL, displayB, NULL);
pthread_create(&thread3_id, NULL, displayC, NULL);
pthread_join(thread1_id, NULL);
pthread_join(thread2_id, NULL);
pthread_join(thread3_id, NULL);
//sem_destroy(&mutex);
printf("n END mainn");
return 0;
}
Thanks you for any help
c multithreading pthreads mutex semaphore
asked Nov 18 '18 at 17:45
John DoeJohn Doe
386
I have a little issue and I don't understand why my code doesn't work.
The purpose of the code is to use 3 different threads to display the sequence:
(abc)*
The output shows only one 'A' ...
sem_t mutex;
char turn = 'a';
void displayA()
{
for(int i = 0; i < 100; i++)
{
sem_wait(&mutex);
if (turn == 'a')
{
printf("A");
turn = "b";
printf("%c", turn);
}
sem_post(&mutex);
}
return NULL;
}
int main()
{
sem_init(&mutex, 0, 1);
pthread_t thread1_id;
pthread_t thread2_id;
pthread_t thread3_id;
pthread_create(&thread1_id, NULL, displayA, NULL);
pthread_create(&thread2_id, NULL, displayB, NULL);
pthread_create(&thread3_id, NULL, displayC, NULL);
pthread_join(thread1_id, NULL);
pthread_join(thread2_id, NULL);
pthread_join(thread3_id, NULL);
//sem_destroy(&mutex);
printf("n END mainn");
return 0;
}
Thanks you for any help
c multithreading pthreads mutex semaphore
c multithreading pthreads mutex semaphore
asked Nov 18 '18 at 17:45
John DoeJohn Doe
386
asked Nov 18 '18 at 17:45
John DoeJohn Doe
386
asked Nov 18 '18 at 17:45
John DoeJohn Doe
386
asked Nov 18 '18 at 17:45
John DoeJohn Doe
386
asked Nov 18 '18 at 17:45
John DoeJohn Doe
386
386
1
Do you want to associate each character to one thread or you just want a thread to print a letter? If it's the second one you just need a simple lock and a character that represents what to print. You acquire the lock, see what you need to print, release the lock. You can also do it (easily) with semaphores. You must also implement the logic to print all other characters in your sequence
– simo-r
Nov 18 '18 at 17:58
1
The code you posted would not compile because it is missingdisplayBanddisplayC. Also,turn = "b"will be flagged. Please post your full code that compiles and links cleanly
– Craig Estey
Nov 18 '18 at 18:10
I couldn't post all my code because it was too long, but the functions displayB and displayC exist:
– John Doe
Nov 18 '18 at 19:13
1
@JohnDoe Posting code that does not compile cleanly is a red flag, indicating to the reader that you are already misinterpreting what you think you're seeing. Post a Minimal, Complete, and Verifiable example. The stackoverflow interface should allow you to post your minimal example program.
– Gil Hamilton
Nov 18 '18 at 22:13
The posted code does not compile! Amongst other things, it is missing the#includestatements needed for the needed header files. Are you expecting us to guess as to which header files are needed?
– user3629249
Nov 18 '18 at 23:22
|
show 4 more comments
1
Do you want to associate each character to one thread or you just want a thread to print a letter? If it's the second one you just need a simple lock and a character that represents what to print. You acquire the lock, see what you need to print, release the lock. You can also do it (easily) with semaphores. You must also implement the logic to print all other characters in your sequence
– simo-r
Nov 18 '18 at 17:58
1
The code you posted would not compile because it is missingdisplayBanddisplayC. Also,turn = "b"will be flagged. Please post your full code that compiles and links cleanly
– Craig Estey
Nov 18 '18 at 18:10
I couldn't post all my code because it was too long, but the functions displayB and displayC exist:
– John Doe
Nov 18 '18 at 19:13
1
@JohnDoe Posting code that does not compile cleanly is a red flag, indicating to the reader that you are already misinterpreting what you think you're seeing. Post a Minimal, Complete, and Verifiable example. The stackoverflow interface should allow you to post your minimal example program.
– Gil Hamilton
Nov 18 '18 at 22:13
The posted code does not compile! Amongst other things, it is missing the#includestatements needed for the needed header files. Are you expecting us to guess as to which header files are needed?
– user3629249
Nov 18 '18 at 23:22
1
1
Do you want to associate each character to one thread or you just want a thread to print a letter? If it's the second one you just need a simple lock and a character that represents what to print. You acquire the lock, see what you need to print, release the lock. You can also do it (easily) with semaphores. You must also implement the logic to print all other characters in your sequence
– simo-r
Nov 18 '18 at 17:58
Do you want to associate each character to one thread or you just want a thread to print a letter? If it's the second one you just need a simple lock and a character that represents what to print. You acquire the lock, see what you need to print, release the lock. You can also do it (easily) with semaphores. You must also implement the logic to print all other characters in your sequence
– simo-r
Nov 18 '18 at 17:58
1
1
The code you posted would not compile because it is missing
displayB and displayC. Also, turn = "b" will be flagged. Please post your full code that compiles and links cleanly– Craig Estey
Nov 18 '18 at 18:10
The code you posted would not compile because it is missing
displayB and displayC. Also, turn = "b" will be flagged. Please post your full code that compiles and links cleanly– Craig Estey
Nov 18 '18 at 18:10
I couldn't post all my code because it was too long, but the functions displayB and displayC exist:
– John Doe
Nov 18 '18 at 19:13
I couldn't post all my code because it was too long, but the functions displayB and displayC exist:
– John Doe
Nov 18 '18 at 19:13
1
1
@JohnDoe Posting code that does not compile cleanly is a red flag, indicating to the reader that you are already misinterpreting what you think you're seeing. Post a Minimal, Complete, and Verifiable example. The stackoverflow interface should allow you to post your minimal example program.
– Gil Hamilton
Nov 18 '18 at 22:13
@JohnDoe Posting code that does not compile cleanly is a red flag, indicating to the reader that you are already misinterpreting what you think you're seeing. Post a Minimal, Complete, and Verifiable example. The stackoverflow interface should allow you to post your minimal example program.
– Gil Hamilton
Nov 18 '18 at 22:13
The posted code does not compile! Amongst other things, it is missing the
#include statements needed for the needed header files. Are you expecting us to guess as to which header files are needed?– user3629249
Nov 18 '18 at 23:22
The posted code does not compile! Amongst other things, it is missing the
#include statements needed for the needed header files. Are you expecting us to guess as to which header files are needed?– user3629249
Nov 18 '18 at 23:22
|
show 4 more comments
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1
Do you want to associate each character to one thread or you just want a thread to print a letter? If it's the second one you just need a simple lock and a character that represents what to print. You acquire the lock, see what you need to print, release the lock. You can also do it (easily) with semaphores. You must also implement the logic to print all other characters in your sequence
– simo-r
Nov 18 '18 at 17:58
1
The code you posted would not compile because it is missing
displayBanddisplayC. Also,turn = "b"will be flagged. Please post your full code that compiles and links cleanly– Craig Estey
Nov 18 '18 at 18:10
I couldn't post all my code because it was too long, but the functions displayB and displayC exist:
– John Doe
Nov 18 '18 at 19:13
1
@JohnDoe Posting code that does not compile cleanly is a red flag, indicating to the reader that you are already misinterpreting what you think you're seeing. Post a Minimal, Complete, and Verifiable example. The stackoverflow interface should allow you to post your minimal example program.
– Gil Hamilton
Nov 18 '18 at 22:13
The posted code does not compile! Amongst other things, it is missing the
#includestatements needed for the needed header files. Are you expecting us to guess as to which header files are needed?– user3629249
Nov 18 '18 at 23:22