How to use pthread_create && mutex?

Posted 2020-10-17 timer_go

1

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

void *thread_function(void *arg)
{
    int i;
    for (i=0; i<5; i++){
        printf("Thread says hi!\n");
        sleep(1);
    }
    return NULL;
}

int main(void)
{
    pthread_t mythread;

    if ( pthread_create( &mythread, NULL, thread_function, NULL) ){
        printf("error creating thread.\n");
        abort();
    }

    if ( pthread_join( mythread, NULL )){
        printf("error joining thread.");
        abort();
    }

    exit(0);
}

gcc -o pthread1 pthread1.c -lpthread

2

#cat thread2.c
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int myglobal;

void *thread_function(void *arg)
{
    int i,j;
    for (i=0; i<20; i++){
        i=myglobal;
        j=j+1;
        printf(".");
        fflush(stdout);
        sleep(1);
        myglobal=j;
    }
    return NULL;
}

int main(void)
{
    pthread_t mythread;
    int i;

    if (pthread_create(&mythread, NULL, thread_function, NULL)){
        printf("Error creating thread.");
        abort();
    }

    for (i=0; i<20; i++){
        myglobal=myglobal+1;
        printf("o");
        fflush(stdout);
        sleep(1);
    }

    if (pthread_join(mythread, NULL)){
        printf("Error joining.");
        abort();
    }

    printf("\nmyglobal equals %d\n ",myglobal);
    exit(0);
}

3. Use mutex

#cat thread3.c
#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <stdlib.h>

int myglobal;

pthread_mutex_t mymutex=PTHREAD_MUTEX_INITIALIZER;

void *thread_function(void *arg)
{
    int i,j;
    for (i=0; i<10; i++){
        pthread_mutex_lock(&mymutex);
        j=myglobal;
        j=j+1;
        printf(".");
        fflush(stdout);
        sleep(1);
        myglobal=j;
        pthread_mutex_unlock(&mymutex);
    }

    return NULL;
}

int main(void)
{
    pthread_t mythread;
    int i;
    if (pthread_create(&mythread, NULL, thread_function, NULL)){
        printf("Error creating function;");
        abort();
    }

    for (i=0; i<10; i++){
        pthread_mutex_lock(&mymutex);
        myglobal=myglobal+1;
        pthread_mutex_unlock(&mymutex);
        printf("o");
        fflush(stdout);
        sleep(1);
    }

    if (pthread_join(mythread, NULL)){
        printf("Error joining thread.");
        abort();
    }

    printf("myglobal equals %d\n",myglobal);
    exit(0);
}

REF

https://www.ibm.com/developerworks/cn/linux/thread/posix_thread2/index.html