Re: lin-lwp and exiting threads

["J. Johnston" <jjohnstn at redhat dot com>]

Daniel Jacobowitz wrote:
> On Tue, Aug 26, 2003 at 01:51:35PM -0400, Daniel Jacobowitz wrote:
>
> > Hi Jeff,
> >
> > I'm doing some work in lin-lwp.c and I saw this bit you recently committed:
> >
> > +      /* Check if the current LWP has previously exited.  For nptl threads,
> > +         there is no exit signal issued for LWPs that are not the
> > +         main thread so we should check whenever the thread is stopped.  */
> > +      if (!lin_lwp_thread_alive (lp->ptid))
> > +       {
> > +         if (in_thread_list (lp->ptid))
> > +           {
> > +             /* Core GDB cannot deal with us deleting the current
> > +                thread.  */
> > +             if (!ptid_equal (lp->ptid, inferior_ptid))
> > +               delete_thread (lp->ptid);
> > +             printf_unfiltered ("[%s exited]\n",
> > +                                target_pid_to_str (lp->ptid));
> > +           }
> > +         if (debug_lin_lwp)
> > +           fprintf_unfiltered (gdb_stdlog,
> > +                               "SWC: %s already exited.\n",
> >                                target_pid_to_str (lp->ptid));
> >
> >
> > This is right after waitpid has returned a non-exiting stopped status for
> > lp->ptid.  Were you just being thorough, or do you have some reason to
> > believe that waitpid would ever return WIFSTOPPED (status) and yet the
> > thread would be dead?

In the early days of nptl, the kernel wasn't always doing what it was
expected to.  This appears to be leftover code as I attempted to ensure we
caught the thread exiting one way or another.

> Also, there's:
>   pid = waitpid (GET_LWP (lp->ptid), &status, 0);
>   if (pid == -1 && errno == ECHILD)
>     {
>       pid = waitpid (GET_LWP (lp->ptid), &status, __WCLONE);
>       if (pid == -1 && errno == ECHILD)
>         {
>           /* The thread has previously exited.  We need to delete it now
>              because in the case of NPTL threads, there won't be an
>              exit event unless it is the main thread.  */
>           if (debug_lin_lwp)
>             fprintf_unfiltered (gdb_stdlog,
>                                 "SWC: %s exited.\n",
>                                 target_pid_to_str (lp->ptid));
>           delete_lwp (lp->ptid);
>           return 0;
>         }
>     }
>   
> Is there some reason you don't also call delete_thread?

Hmm, appears to be an oversight on my part.

Do you want to make these changes?

-- Jeff J.