linux - Thread management in a cloned process with CLONE_VM flag set -

i need thread management inside cloned process. point need create , destroy threads inside cloned process asynchronously (pthread_cancel_asynchronous set). fine if clone_vm not set, need because main , child process must share same address space. below example demonstrate question. being compiled clone_vm flag program hangs @ pthread_join while without clone_vm fine. there ways deal problem?

p.s. tried @ debian gnu/linux versions 7,8 , unstable (kernels 3.2, 3.16, 4.0).

#include <stdlib.h> #include <stdio.h> #include <unistd.h> #include <pthread.h> #include <sched.h> #include <string.h> #include <signal.h> #include <sys/types.h> #include <sys/wait.h>  /* compile # gcc -o pthread_test -lpthread pthread_test.c */  #define clone 1  pthread_mutex_t mutex = pthread_mutex_initializer;  void *thread_test(void *unused) {     pthread_setcanceltype(pthread_cancel_asynchronous, null);     pthread_setcancelstate(pthread_cancel_enable, null);     pthread_mutex_unlock(&mutex);     pause();     return null; }  int test(void *unused) {     void *status;     int r;     pthread_t thread;     pthread_mutex_lock(&mutex);     if ((r = pthread_create(&thread, null, thread_test, null)) != 0) {         printf("pthread_create returned %d\n", r);         exit(1);     }     pthread_mutex_lock(&mutex);     printf("cancelling thread\n");     r = pthread_cancel(thread);     printf("pthread cancel returned : %s(%d)\n", strerror(r), r);     printf("joining thread\n");     r = pthread_join(thread, &status);     printf("pthread_join returned : %s\n", strerror(r));     if (status == pthread_canceled)         printf("child canceled\n");     else         printf("child exit status %u\n", (unsigned)status);      return 0; }  int main(void) { #if clone     void *stack = (void *)malloc(16384);     if (clone(test, stack + 16383, clone_vm | clone_fs | clone_files, null) < 0) {         printf("clone failed\n");         exit(1);     }     waitpid(0, null, __wclone);     return 0; #else     void *stack = (void *)malloc(16384);     if (clone(test, stack + 16383, /*clone_vm |*/ clone_fs | clone_files, null) < 0) {         printf("clone failed\n");         exit(1);     }     waitpid(0, null, __wclone);     return 0; #endif }