Re: [Qemu-devel] [PATCH] gdbstub: do not restart crashed guest

[Luiz Capitulino <lcapitulino@redhat.com>]

On Thu, 30 May 2013 13:55:50 +0200
Laszlo Ersek <lersek@redhat.com> wrote:

> On 05/30/13 13:20, Paolo Bonzini wrote:
> > If a guest has crashed with an internal error or similar, detaching
> > gdb (or any other debugger action) should not restart it.
> > 
> > Cc: Jan Kiszka <jan.kiszka@siemens.com>
> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> > ---
> >  gdbstub.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/gdbstub.c b/gdbstub.c
> > index e80e1d3..90e54cb 100644
> > --- a/gdbstub.c
> > +++ b/gdbstub.c
> > @@ -371,7 +371,9 @@ static inline void gdb_continue(GDBState *s)
> >  #ifdef CONFIG_USER_ONLY
> >      s->running_state = 1;
> >  #else
> > -    vm_start();
> > +    if (runstate_check(RUN_STATE_DEBUG)) {
> > +        vm_start();
> > +    }
> >  #endif
> >  }
> >  
> > 
> 
> I sought to check the gdb_continue() call sites, and uses of
> RUN_STATE_DEBUG. Seems reasonable.
> 
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> 
> (
> FWIW I wonder why in commit ad02b96a Luiz allowed DEBUG -> SUSPENDED. As
> far as I understand, when the debugger is attached, the guest is not
> running, hence it can't go directly to RUN_STATE_SUSPENDED. Maybe due to
> a concurrent monitor command?

I honestly don't remember if I took into account the explanation you gave
below. You're right that a stopped guest can't suspend.

> 
> Technically it does seem possible; from main_loop_should_exit():
> 
>     if (qemu_debug_requested()) {
>         vm_stop(RUN_STATE_DEBUG);
>     }
>     if (qemu_suspend_requested()) {
>         qemu_system_suspend();
>     }
> 
> Both requests could become pending during one iteration of the loop, and
> the next iteration will see both of them. OK.
> )
> 
> Laszlo
>