This is the mail archive of the
gdb-patches@sourceware.org
mailing list for the GDB project.
Re: [RFA] Make continuations per-thread.
- From: Pedro Alves <pedro at codesourcery dot com>
- To: "Ulrich Weigand" <uweigand at de dot ibm dot com>
- Cc: Daniel Jacobowitz <drow at false dot org>, Vladimir Prus <vladimir at codesourcery dot com>, gdb-patches at sourceware dot org
- Date: Tue, 6 May 2008 19:11:52 +0100
- Subject: Re: [RFA] Make continuations per-thread.
- References: <200805021519.m42FJ6bd009452@d12av02.megacenter.de.ibm.com>
A Friday 02 May 2008 16:19:06, Ulrich Weigand wrote:
> Note that current GDB is really broken when it comes to handling
> step / next operations that are interrupted by an event in some
> other thread. There is some code to "context switch" the stepping
> status, but this appears to be incomplete, and leads to inconsistent
> results; e.g. GDB can run into internal assertion failures like
> "Thread Event Breakpoint: gdb should not stop!" (see PR 2250).
>
> I'm currently carrying the following patch in our GDB builds that
> fixes the issue be ensuring:
>
Thanks for showing us that.
> - If the step operation is interrupted by an *internal* breakpoint
> that is handled transparently, the operation continues in a
> transparent and consistent manner after the breakpoint was handled.
>
> - If the step operation is interrupted by an *explicit* breakpoint
> that breaks to a user prompt, it is completely cancelled. It is
> then up to the user how to continue from the prompt.
>
A agree that this behaviour is sensible in all-stop
(what we have now) mode. I tried your patch, and the bahaviour
makes sense to me.
Note, however, that in non-stop mode, we need to retain the
stepping state per-thread (and actually make a
few more things per-thread), so we'd like to keep the variables
you're removing from struct thread_info in some form.
http://sourceware.org/ml/gdb-patches/2008-05/msg00232.html
> Now it looks like the second point is in conflict to the goal you
> are proposing here (namely, that even after a user prompt, the
> interrupted step/next/finish still continues in some manner).
> I'm not sure how this could be accomplished ...
>
Our major goal is to have that in non-stop mode. It seemed
we would win some of it for free in all-stop mode, but it
turned out it isn't so.
Thanks!
--
Pedro Alves