c - The thread created by pthread_create the same with the kernel thread?

Question

I use the command below to view the maximum number of threads my system allows:

# cat /proc/sys/kernel/threads-max

And the number is 772432.

However, I use the code below to create 1 million threads. And it works.

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

static unsigned long long thread_nr = 0;

pthread_mutex_t mutex_;

void* inc_thread_nr(void* arg) {
    /* int arr[1024][1024]; */
    (void*)arg;
    pthread_mutex_lock(&mutex_);
    thread_nr ++;
    pthread_mutex_unlock(&mutex_);
}

int main(int argc, char *argv[])
{
    int err;
    int cnt = 0;

    pthread_mutex_init(&mutex_, NULL);

    while (cnt < 1000000) {
        pthread_t pid;
        err = pthread_create(&pid, NULL, (void*)inc_thread_nr, NULL);
        if (err != 0) {
            break;
        }
        pthread_join(pid, NULL);
        cnt++;
    }

    pthread_mutex_destroy(&mutex_);
    printf("Maximum number of threads per process is = %d
", thread_nr);
}

The output is :

Maximum number of threads per process is = 1000000

which is larger than the maximum number of threads. What is the reason for this? And is the thread create by pthread_create the same with the kernel thread?

My OS is Fedora 16, with 12 cores, 48G RAM.

Answer 1

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