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Re: [Patch] Use resume instead of target_resume when stepping over watchpoint.
- From: Pedro Alves <pedro at codesourcery dot com>
- To: gdb-patches at sourceware dot org
- Cc: Joel Brobecker <brobecker at adacore dot com>, David Daney <ddaney at avtrex dot com>
- Date: Thu, 30 Oct 2008 12:22:23 +0000
- Subject: Re: [Patch] Use resume instead of target_resume when stepping over watchpoint.
- References: <48C71565.3050601@avtrex.com> <20081030030805.GC3635@adacore.com>
On Thursday 30 October 2008 03:08:05, Joel Brobecker wrote:
> Pedro, Others,
>
> What do you think of this patch? Personally, I have pretty much
> convinced myself that it shouldn't do any harm, but I really
> wished that "resume" would take a ptid as an argument. Except
> that this is not trivial to do, and I think that the current
> "resume" would need to be split a bit, to remove the code that
> determines what to resume.
Won't this slightly change the behaviour on hardware single-step
archs? Before, we'd always tell the target to resume a single-thread
(keeping the others stopped, on target that support scheduler locking);
with this change, I think you'll tell the target to resume all
threads.
Urglhs, infrun could use a facelift. The natural function
to call would be keep_going instead of resume/prepare_to_wait,
but keep_going doesn't know a think about watchpoints...
Would setting ecs->event_thread->trap_expected = 1 in addition
to switching to resume so we trigger this:
resume:
if ((step || singlestep_breakpoints_inserted_p)
&& tp->trap_expected)
{
...
resume_ptid = inferior_ptid;
}
be too ugly? Hmmm, maybe not OK, it can have other side
effects, like tripping on this...
if (ecs->event_thread->stop_signal == TARGET_SIGNAL_TRAP
&& ecs->event_thread->trap_expected
&& gdbarch_single_step_through_delay_p (current_gdbarch)
&& currently_stepping (ecs->event_thread))
{
Can you confirm what I think I'm seeing?
>
> Anyway, I don't see anything wrong with this patch, but I'd love
> for someone to take a look as well. This is a pretty delicate
> part of the debugger. Do we really need the gdb_assert thought?
>
> On Tue, Sep 09, 2008 at 05:31:33PM -0700, David Daney wrote:
> > In handle_inferior_event() when stepping over a watch point currently we
> > issue target_resume(). This only works on architectures that have
> > hardware single step support. For gdbarch_software_single_step_p()
> > systems (like MIPS), we need to insert a single step breakpoint instead.
> >
> > The fix is to call resume() as it does the right thing already. I also
> > added an assert that inferior_ptid == ecs->ptid to be sure that resume()
> > was stepping the proper thread.
> >
> > This is essentially the change requested by Daniel in:
> > http://sourceware.org/ml/gdb-patches/2008-04/msg00443.html
> >
> > This change is a prerequisite for my forthcoming MIPS hardware watch patch.
> >
> > Tested on x86_64-pc-linux-gnu as well as mipsel-linux (in conjunction
> > with the MIPS hardware watch patch).
> >
> > OK to commit?
> >
> > 2008-09-09 David Daney <ddaney@avtrex.com>
> >
> > * infrun.c (handle_inferior_event): Call resume instead of
> > target_resume when stepping over watchpoint.
> >
> >
>
> > Index: infrun.c
> > ===================================================================
> > RCS file: /cvs/src/src/gdb/infrun.c,v
> > retrieving revision 1.316
> > diff -u -p -r1.316 infrun.c
> > --- infrun.c 8 Sep 2008 22:10:20 -0000 1.316
> > +++ infrun.c 9 Sep 2008 23:37:09 -0000
> > @@ -2472,7 +2472,8 @@ targets should add new threads to the th
> > if (!HAVE_STEPPABLE_WATCHPOINT)
> > remove_breakpoints ();
> > registers_changed ();
> > - target_resume (ecs->ptid, 1, TARGET_SIGNAL_0); /* Single step */
> > + gdb_assert (ptid_equal (inferior_ptid, ecs->ptid));
> > + resume (1, TARGET_SIGNAL_0); /* Single step */
> > waiton_ptid = ecs->ptid;
> > if (HAVE_STEPPABLE_WATCHPOINT)
> > infwait_state = infwait_step_watch_state;
>
>
--
Pedro Alves