posix semaphores posting for more than one thread at a time

Hello All,

I would like to know can we post more than one thread at a time.

I have code like below

Code:

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#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>

#include <pthread.h>
#include <semaphore.h>

#define MAX_MSG_LEN 256

sem_t sem1;

char msg1[MAX_MSG_LEN] = "1";

void *thrdFun1(void *arg);

int main()
{
    pthread_t thrd1,thrd2,thrd3,thrd4;
    char argmsg1[] = "Thread1: ";
    char argmsg2[] = "Thread2: ";
    char argmsg3[] = "Thread3: ";
    char argmsg4[] = "Thread4: ";
    int res;
    int thNum;

    res = sem_init(&sem1,0,0);
    res = pthread_create(&thrd1, NULL, thrdFun1, argmsg1);
    res = pthread_create(&thrd2, NULL, thrdFun1, argmsg2);
    res = pthread_create(&thrd3, NULL, thrdFun1, argmsg3);
    res = pthread_create(&thrd4, NULL, thrdFun1, argmsg4);

    while(1)
    {
          printf("Enter message to end to thread \n");
          fgets(msg1,MAX_MSG_LEN,stdin);
          sem_post(&sem1);
    }

    return 0;          /* writing the comments */
}

void *thrdFun1(void *arg)
{
    while(1)
    {
          sem_wait(&sem1);
          printf("Iam %s message is %s\n",arg,msg1);
    }
}

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here it does accept and sem_post serially to the thread than invoking all the threads at a time.

Do this kind of behaviour can be achived using posix semaphores ( posting to multiple threads)? or should i use any pthread api like pthread_broadcast etc..

your comments would help in understanding .

regards

>> invoking all the threads at a time ... can be achieved using posix semaphores?
No.

Using pthread_cond_broadcast(), you can wake all threads that are currently waiting on a condition variable.

gg

thx codeplug for taking time,

i missed a basic concept here while posting ..! iam creating the binary semaphore so it can be accessed only one thread at a time.

Even if i create the sem phore object with 4 tokens.

It does wait in the first thread it self.

I think I have to read more about pthreads/semaphores .

thanx any way ..

You already asked this question

http://cboard.cprogramming.com/linux...er-thread.html

I also couldn't help but not know exactly what your trying to achieve.

Quote:

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I would like to know can we post more than one thread at a time.

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Quote:

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am creating the binary semaphore so it can be accessed only one thread at a time.

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That sounds contradictory. Are you wanting each thread to only run one at a time but for each one to run one after another?