[PATCH] sandbox: also restore terminal settings when killed by SIGINT

[Simon Glass]

On Fri, 14 Feb 2020 at 03:58, Rasmus Villemoes
<rasmus.villemoes at prevas.dk> wrote:
>
> Hitting Ctrl-C is a documented way to exit the sandbox, but it is not
> actually equivalent to the reset command. The latter, since it follows
> normal process exit, takes care to reset terminal settings and
> restoring the O_NONBLOCK behaviour of stdin (and, in a terminal, that
> is usually the same file description as stdout and stderr, i.e. some
> /dev/pts/NN).
>
> Failure to restore (remove) O_NONBLOCK from stdout/stderr can cause
> very surprising and hard to debug problems back in the terminal. For
> example, I had "make -j8" consistently failing without much
> information about just exactly what went wrong, but sometimes I did
> get a "echo: write error". I was at first afraid my disk was getting
> bad, but then a simple "dmesg" _also_ failed with write error - so it
> was writing to the terminal that was buggered. And both "make -j8" and
> dmesg in another terminal window worked just fine.
>
> So install a SIGINT handler so that if the chosen terminal
> mode (cooked or raw-with-sigs) means Ctrl-C sends a SIGINT, we will
> still call os_fd_restore(), then reraise the signal and die as usual
> from SIGINT.
>
> Before:
>
> $ grep flags /proc/$$/fdinfo/1
> flags:  0102002
> $ ./u-boot
> # hit Ctrl-C
> $ grep flags /proc/$$/fdinfo/1
> flags:  0106002
>
> After:
>
> $ grep flags /proc/$$/fdinfo/1
> flags:  0102002
> $ ./u-boot
> # hit Ctrl-C
> $ grep flags /proc/$$/fdinfo/1
> flags:  0102002
>
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
> ---
>  arch/sandbox/cpu/os.c | 9 +++++++++
>  1 file changed, 9 insertions(+)

Nice explanation, thank you.

Reviewed-by: Simon Glass <sjg at chromium.org>