Bug 17467

It's hard to tell without your program. Can you post the source?

I'm sorry I didn't post this info originally, but I was away from my home box. 
The relevant version numbers are:
  kernel-source-2.2.16-3
  libc-5.3.12-31
  glibc-2.1.3-21

The source that I was getting the errors with is:

#include <unistd.h>
#include <sched.h>
#include <sys/types.h>
#include <stdlib.h>

int do_something() {
   printf("start clone\n");
   printf("Clone closes\n");
   exit(0);
}

int main(int argc, char *argv[]) {
   pid_t chpid;
   void **child_stack;

   printf("MALLOC\n");
   child_stack = (void **) malloc(16384);
   printf("Address of stack = %d\n", (int)child_stack);
   printf("CLONE\n");
   chpid = clone(do_something, child_stack, CLONE_VM|CLONE_FILES, NULL);
   printf("Parent pid = %d\n", getpid());
   printf("Child pid = %d\n", chpid);
   sleep(1);
   printf("Parent closes\n");
   return 0;
}
      
It shows the PID's of the parent and child, the child prints its first line, 
then when the parent sleeps, the child also sleeps. The parent then wakes up, 
prints its last line and exits. At this point, the child has not finished yet, 
so I get a seg-fault and a core dump. I know this works on other linux 
distributions, so I'm not sure what to do next. Any ideas?

You cannot mix the glibc printf type functions with clone safely. They assume
you use the pthread wrappers and interface. Try using write() and _exit

The problems with printf are not relevant here. The problem involves context 
switching between the parent and child.  I have successfully used this program 
on another machine (winlinux2000) with kernel 2.2.13 and glibc 2.1.2.  Could 
you please verify whether this is an actual bug or not?  I do not have a second 
machine with Redhat 6.2 installed to test it on. If this is not an actual bug, 
then my system has been damaged somehow, and I should reinstall.  If it is a 
bug, then there is something wrong with either the kernel, or the libraries 
shipped with Redhat 6.2.

The problem is not using pthreads but using pthread assuming libraries. printf
isnt safe the way you use it, exit isnt the right call and the library unwind
code will drop your dlsyms before the other  thread uses them. libc expects you
access it in standards compliant ways.

(rebuild it -static with no printf/exit calls and you'll find it works for
example)

Thank you for the help. This is the very reason I'm writing this article, for 
people like me who don't realize the ins and outs of problems like this.  Would 
you have any suggestions of other things I should cover in this article?  
Anything else you think might trip up other beginning programmers?