Posix Pthread mutual exclusion

Question

I have written my issue in comments in the code.

I am trying to make my code parallel by using pthreads. First I want to write a bulk of data in memory by several threads in parallel. After writing the data, I want to execute this data by same threads. And after executing the data, I want to read it. And after these three operations, I want to pass this data to other files. And I want to repeat this process several times.

I would really appreciate any of your help. Thank you.

#include <pthread.h>
#include <stdio.h>

#define ARRAYSIZE 100
#define NUMTHREADS 7

struct ThreadData {
    int start, stop, id;
    int* array;
};

/* function to write, execute and read data */
void* cal(void* td) {
    struct ThreadData* data=(struct ThreadData*) td;
    int start=data->start;
    int stop=data->stop;
    int thread_id = data ->id;
    int i,s, counter;
    counter = 0;

    //main loop
    for (s=0; s<200; s++){

        // in this loop1, I want to write data here by all the threads
        for (i=start; i<stop; i++) {
    printf("thread %d is writing data\n", thread_id);
        }

        //in this loop2, after data written by all the threads in loop1,
        // data is execuated by all threads in this loop2 
        for (i=start; i<stop; i++) {
    printf("thread %d is executing data\n", thread_id);
        }

        //in this loop3, data is read after completion of 
        // writing and execution in loop1 and loop2
        for (i=start; i<stop; i++) {
    printf("thread %d is reading data\n", thread_id);
        }

        // counter, I want this counter to be executed only once 
        // per iteration after writing, executing and reading data.
        counter = counter +1;
    printf ("Value of counter is %d\n", counter); 

    }

    return NULL;
}

int main(void) {
    int array[ARRAYSIZE];
    pthread_t thread[NUMTHREADS];
    struct ThreadData data[NUMTHREADS];
    int i;

    int tasksPerThread=(ARRAYSIZE+NUMTHREADS-1)/NUMTHREADS;

    /* Divide work for threads, prepare parameters */
    for (i=0; i<NUMTHREADS; i++) {
        data[i].start=i*tasksPerThread;
        data[i].stop=(i+1)*tasksPerThread;
        data[i].array=array;
        data[i].id = i;
    }
    /* the last thread must not go past the end of the array */
    data[NUMTHREADS-1].stop=ARRAYSIZE;

    /* Launch Threads */
    for (i=0; i<NUMTHREADS; i++) {
        pthread_create(&thread[i], NULL, cal, &data[i]);
    }

    /* Wait for Threads to Finish */
    for (i=0; i<NUMTHREADS; i++) {
        pthread_join(thread[i], NULL);
    }

    return 0;
}

Answer 1

I think you need mutual exclusion only for counter so do a thread synchronization step before it and that should be enough.