Re: [Xen-devel] [PATCH v2 1/2] tools/console: reset tty when xenconsole fails

[Anthony Liguori <anthony@xxxxxxxxxxxxx>]

On Tue, Mar 18, 2014 at 11:00 AM, Ian Jackson <ian.jackson@xxxxxxxxxxxxx> wrote:
> If xenconsole (the client program) fails, it calls err.  This would
> previously neglect to reset the user's terminal to sanity.  Use atexit
> to do so.
>
> This routinely happens in Xen 4.4 RC5 with pygrub because libxl
> writes the value "" to the tty xenstore key when using xenconsole.
> After this patch this just results in a harmless error message.
>
> Reported-by: M A Young <m.a.young@xxxxxxxxxxxx>
> Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> CC: M A Young <m.a.young@xxxxxxxxxxxx>
> CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
> Acked-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
>
> ---
> v2: Fix whitespace error (reintroduce hard tab)
>     Fix commit message not to claim ignorance about root cause
> ---
>  tools/console/client/main.c |   11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/tools/console/client/main.c b/tools/console/client/main.c
> index eb6a1a9..7ce4f24 100644
> --- a/tools/console/client/main.c
> +++ b/tools/console/client/main.c
> @@ -257,6 +257,13 @@ typedef enum {
>         CONSOLE_SERIAL,
>  } console_type;
>
> +static struct termios stdin_old_attr;
> +
> +static void restore_term_stdin(void)
> +{
> +       restore_term(STDIN_FILENO, &stdin_old_attr);
> +}
> +
>  int main(int argc, char **argv)
>  {
>         struct termios attr;
> @@ -383,9 +390,9 @@ int main(int argc, char **argv)
>         }
>
>         init_term(spty, &attr);
> -       init_term(STDIN_FILENO, &attr);
> +       init_term(STDIN_FILENO, &stdin_old_attr);
> +       atexit(restore_term_stdin); /* if this fails, oh dear */

You may want to consider using a signal handler too.  atexit() isn't
called when exiting due to SIGTERM or SIGSEGV.

Regards,

Anthony Liguori

>         console_loop(spty, xs, path);
> -       restore_term(STDIN_FILENO, &attr);
>
>         free(path);
>         free(dom_path);
> --
> 1.7.10.4
>
>
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