Re: [3/7] Adjust the bsd-uthread target

Pedro Alves
2008-08-08T22:42:13Z

A Friday 08 August 2008 22:51:25, Mark Kettenis escreveu:
> > From: Pedro Alves <pedro@codesourcery.com>
> > Date: Fri, 8 Aug 2008 02:36:03 +0100
> >
> > This patch adjusts the bsd-uthread target to use thread_change_ptid,
> > and to never let the core see an event happen in a thread not in
> > the thread table.
> >
> > Tested on i386-unknown-freebsd6.0 with a little hack in the
> > testsuite to link the gdb.thread tests against -lc_r instead
> > of -lpthread, and on i386-unknown-openbsd4.3, where no hack is
> > needed.
> >
> > This patch depends on patch 1 and 2.
> >
> > OK?
> >
> > Index: src/gdb/bsd-uthread.c
> > ===================================================================
> > --- src.orig/gdb/bsd-uthread.c 2008-07-29 12:06:38.000000000 +0100
> > +++ src/gdb/bsd-uthread.c 2008-07-29 12:17:34.000000000 +0100
> > @@ -413,7 +415,7 @@ bsd_uthread_find_new_threads (void)
> > {
> > ptid_t ptid = ptid_build (pid, 0, addr);
> >

> > - if (!in_thread_list (ptid))
> > + if (!in_thread_list (ptid) || is_exited (ptid))
> > add_thread (ptid);
>
> This doesn't make sense to me. You're adding a threadhere that's no
> longer there?

The "exited" state is what you get *after* you delete_thread the current
thread (inferior_ptid). We don't delete the thread from the thread list
in that case, but instead tag it as "exited". It means the thread list
is still holding reference to a thread that has already exited.
If you're seeing an event with a ptid equal to an "exited" thread,
this is the OS reusing the ptid, but, it's a new thread, which
should get a new gdb thread id, so things like thread
specific breakpoints don't think this was the same thread, both the
CLI user or MI see a "new thread event", etc. add_thread handles
that case internally. This means it is now safe to delete_thread
(inferior_ptid), regarding context-switching, and infrun state. It
wasn't a couple of weeks ago.

--
Pedro Alves