No thread created despite success on return from pthread_create()

Question

I have written quite a lot of threaded code on HP-UX and even SUSE and that works perfectly. But it does not work on Red Hat. This is my machine:

Linux version 3.10.0-1062.18.1.el7.x86_64 (Red Hat 4.8.5-39)

Red_Hat_Enterprise_Linux-Release_Notes-7-en-US-7-2.el7.noarch

redhat-release-server-7.7-10.el7.x86_64

I wrote a simple test program, thr_ex.c:

#include <pthread.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>



void *funny(void *);



void *funny(s)
void *s;

{ 
    int fd;


    fd = creat("/tmp/funny_func", 0600);

    write(fd, s, strlen((char *) s));

    close(fd);
}



int main()

{
    int                 return_value;
    pthread_t           thread_id;
    pthread_attr_t      thread_attr;


    pthread_attr_init(&thread_attr);
    pthread_attr_setscope(&thread_attr, PTHREAD_SCOPE_SYSTEM);
    pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);

    return_value = pthread_create(&thread_id, &thread_attr, funny, (void *) "Here I am\n");

    printf("Return value == %d\n", return_value);
    printf("Thread id    == %hu\n", thread_id);

    exit(0);
} /* End main. */

Compiling, building:

gcc -pthread -s -o thr_ex thr_ex.c

Running:

./thr_ex

Return value == 0

Thread id == 5888

But no file gets created under /tmp. strace -f shows no creat() or write() ( except from the printf's in main () ).

However, strace -f do show, for example: strace: Exit of unknown pid 64574 ignored

I have tried even simpler code where the thread only runs a printf() and a fflush(), with no thread attributes and no argument to the function. Still nothing happens.

Answer 1

Insert before the return statement or exit( 0 ) statement in main

pthread_exit( NULL );

Otherwise the created thread can have no time to be executed because the process will end.