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Re: RFA[threads]: Fork event updates, part the thirteenth
- From: Daniel Jacobowitz <drow at mvista dot com>
- To: Michael Snyder <msnyder at redhat dot com>
- Cc: gdb-patches at sources dot redhat dot com, kettenis at gnu dot org
- Date: Mon, 6 Jan 2003 19:50:55 -0500
- Subject: Re: RFA[threads]: Fork event updates, part the thirteenth
- References: <20021215213952.GA3923@nevyn.them.org> <3E1A1710.7E0B931@redhat.com>
On Mon, Jan 06, 2003 at 03:53:52PM -0800, Michael Snyder wrote:
> Daniel Jacobowitz wrote:
> >
> > Now is where it starts to get interesting. Michael, I mentioned this patch
> > to you at lunch last week. If you take a short-lived program, run it, and
> > detach it, and run it again, you'll see the exit of the _previous_ copy.
> > Then GDB gets hopelessly confused. I have a testcase for this which I'll
> > post in a moment.
> >
> > The reason it's included here is that that's essentially what happens if you
> > are using "set follow-fork-mode child". We detach from the parent, which
> > exits, confusing GDB.
> >
> > Is this OK?
>
> Hi Dan,
>
> Please excuse the delay. This seems OK. In child_wait,
> would it be possible to add a check to see if the exiting
> process is in our lwp list?
I _think_ that child_wait will never be called if there is anything in
the LWP list; if we have LWPs, we'll have pushed thread_db onto the
stack, and we'll go to lin_lwp_wait instead if thre are any LWPs. But
I'm sleepy, so I may be missing something; I'll sit on this and look at
it again tomorrow :)
Thanks.
> > 2002-12-15 Daniel Jacobowitz <drow@mvista.com>
> >
> > * lin-lwp.c (child_wait): Ignore exit statuses for processes other
> > than inferior_ptid.
> > (lin_lwp_wait): Ignore exit statuses for unknown LWPs.
> >
> > Index: lin-lwp.c
> > ===================================================================
> > RCS file: /cvs/src/src/gdb/lin-lwp.c,v
> > retrieving revision 1.39
> > diff -u -p -r1.39 lin-lwp.c
> > --- lin-lwp.c 9 Dec 2002 18:41:42 -0000 1.39
> > +++ lin-lwp.c 15 Dec 2002 21:16:34 -0000
> > @@ -964,6 +964,14 @@ child_wait (ptid_t ptid, struct target_w
> > pid = waitpid (GET_PID (ptid), &status, __WCLONE);
> > save_errno = errno;
> >
> > + /* Make sure we don't report an event for the exit of the
> > + original program, if we've detached from it. */
> > + if (pid != -1 && ! WIFSTOPPED (status) && pid != GET_PID (inferior_ptid))
> > + {
> > + pid = -1;
> > + save_errno = EINTR;
> > + }
> > +
> > clear_sigio_trap ();
> > clear_sigint_trap ();
> > }
> > @@ -1091,6 +1099,17 @@ lin_lwp_wait (ptid_t ptid, struct target
> > gdb_assert (pid == -1 || lwpid == pid);
> >
> > lp = find_lwp_pid (pid_to_ptid (lwpid));
> > +
> > + /* Make sure we don't report an event for the exit of an LWP not in
> > + our list, i.e. not part of the current process. This can happen
> > + if we detach from a program we original forked and then it
> > + exits. */
> > + if (! WIFSTOPPED (status) && ! lp)
> > + {
> > + status = 0;
> > + continue;
> > + }
> > +
> > if (! lp)
> > {
> > lp = add_lwp (BUILD_LWP (lwpid, GET_PID (inferior_ptid)));
>
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer