Re: Using one ups to follow a child

From: Bob Carragher (dancebob_at_mindspring.com)
Date: Wed May 22 2002 - 06:06:35 BST

  • Next message: Rod Armstrong: "Ups 3.37 released" 
    Rod Armstrong <rod_at_san-jose.tt.slb.com> sez:

> I forgot to add that one can follow the child using just one instance of
> ups if you want:
> 
> 1. ups parent &
>    The parent code did this:
>   if((child_pid = vfork()) == FALSE)
>   {                            
>     /* this is the child */
>     ....
>   }
>   else
>   {
>     /* this is the parent */
>     kill(child_pid, 23);       <<< insert this breakpoint code. 23 is SIGSTOP
>     printf("child pid is %d\n", child_pid);  << breakpoint code to get pid
>     ....
>   }
>   #stop;  <<<<<<<<< stop here to follow the child
> 
> 2. At the #stop, edit the target name to the child name, press RET.
> 
> 3. Attach to the <pid>.
> 
> 4. From an xterm, continue the child:
>    kill -CONT <pid>
> 
> 5. In ups, put a break on main() or whatever, and continue.

Okay, now I'm intrigued by whether this can be done to enable
ups to follow threads under Linux.

Some may remember that I asked about this at the beginning of
this year.  Basically, ups will hang under Linux if a breakpoint
is enabled in code that is normally run under a created thread.
(Actually, I finally traced the code a bit.  It hangs at the call
to wait() on line 215 of ao_ptrace.c.)

I realize the fix is not simple, otherwise it would've been done
by now, but I'm curious as to whether anyone knows what is going
on, and whether I can insert workarounds in my code.

Thanks!

				Bob

    This archive was generated by hypermail 2.1.4 : Thu May 23 2002 - 15:54:16 BST