Re: [PATCH v2 3/3] gdbstub: replace exit(0) with proper shutdown

[Clément Chigot]

On Mon, Sep 4, 2023 at 11:23 AM Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Wed, 23 Aug 2023 at 08:07, Clément Chigot <chigot@adacore.com> wrote:
> >
> > This replaces the exit(0) call by a shutdown request, ensuring a proper
> > cleanup of Qemu. Otherwise, some connections could be broken without
> > being correctly flushed.
> >
> > Signed-off-by: Clément Chigot <chigot@adacore.com>
> > ---
> >  gdbstub/gdbstub.c |  3 +--
> >  gdbstub/softmmu.c | 13 +++++++++++++
> >  gdbstub/user.c    |  2 ++
> >  3 files changed, 16 insertions(+), 2 deletions(-)
> >
> > diff --git a/gdbstub/gdbstub.c b/gdbstub/gdbstub.c
> > index 5f28d5cf57..358eed1935 100644
> > --- a/gdbstub/gdbstub.c
> > +++ b/gdbstub/gdbstub.c
> > @@ -1298,7 +1298,6 @@ static void handle_v_kill(GArray *params, void 
> > *user_ctx)
> >      gdb_put_packet("OK");
> >      error_report("QEMU: Terminated via GDBstub");
> >      gdb_exit(0);
> > -    exit(0);
> >  }
> >
> >  static const GdbCmdParseEntry gdb_v_commands_table[] = {
> > @@ -1818,7 +1817,7 @@ static int gdb_handle_packet(const char *line_buf)
> >          /* Kill the target */
> >          error_report("QEMU: Terminated via GDBstub");
> >          gdb_exit(0);
> > -        exit(0);
> > +        break;
> >      case 'D':
> >          {
> >              static const GdbCmdParseEntry detach_cmd_desc = {
> > diff --git a/gdbstub/softmmu.c b/gdbstub/softmmu.c
> > index f509b7285d..fa9b09537d 100644
> > --- a/gdbstub/softmmu.c
> > +++ b/gdbstub/softmmu.c
> > @@ -434,6 +434,19 @@ void gdb_exit(int code)
> >      }
> >
> >      qemu_chr_fe_deinit(&gdbserver_system_state.chr, true);
> > +
> > +    /*
> > +     * Shutdown request is a clean way to stop the QEMU, compared
> > +     * to a direct call to exit(). But we can't pass the exit code
> > +     * through it so avoid doing that when it can matter.
> > +     * As this function is also called during the cleanup process,
> > +     * avoid sending the request if one is already set.
> > +     */
> > +    if (code) {
> > +        exit(code);
> > +    } else if (!qemu_shutdown_requested_get()) {
> > +        qemu_system_shutdown_request(SHUTDOWN_CAUSE_GUEST_SHUTDOWN);
> > +    }
> >  }
>
> This definitely doesn't look right. Either exit() is OK
> to call, or it is not. We shouldn't be exiting one way
> if the exit status is 0 and another way if it is non-0.

I do agree but AFAIK, this isn't possible to pass the exit code using
qemu_system_shutdown_request.
Would it make more sense to trigger a SHUTDOWN_CAUSE_GUEST_PANIC
instead ? This would result in a non-0 exit code and the already
available gdb_trace would show the real exit code if needed.

Clément