On Tue, Dec 29, 2020 at 04:53:26PM +0800, zhangqiumi...@huawei.com wrote:
> From: zhangqiumiao <zhangqiumi...@huawei.com>
>
> Since ttySx and ttyAMAx are low-speed devices, serial port writing will be
> suspended when the buffer of driver layer is full due to serial port damage.
> The
> concrete representation is n_tty_write blocking in the process of wait_woken,
> the process of writing serial port exists without feedback, and becomes a
> zombie
> process. So for ttySx and ttyAMAx, set the timeout value of wait_woken
> function
> to 60s. Wake up and flush the buffer after timeout.
>
> Signed-off-by: zhangqiumiao <zhangqiumi...@huawei.com>
Please use your "real name" here and the From line.
And since when is ttySx always a "low speed" device?
And what do you mean by "damage"?
> ---
> drivers/tty/Kconfig | 8 ++++++++
> drivers/tty/n_tty.c | 19 +++++++++++++++++++
> 2 files changed, 27 insertions(+)
>
> diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
> index 47a6e42..cc33c8b 100644
> --- a/drivers/tty/Kconfig
> +++ b/drivers/tty/Kconfig
> @@ -173,6 +173,14 @@ config LDISC_AUTOLOAD
> dev.tty.ldisc_autoload sysctl, this configuration option will
> only set the default value of this functionality.
>
> +config TTY_CONSOLE_STABLE
> + bool "Enhance serial console stability"
> + help
> + Set the timeout value of wait_woken function to 60s, wake up and
> + flush the buffer after timeout. It can prevent the serial port
> + from falling into loopback waiting when the serial port is damaged
> + and enhance the stability of serial console.
No config option should be needed for "make the kernel more stable" type
of options, right?
> +
> source "drivers/tty/serial/Kconfig"
>
> config SERIAL_NONSTANDARD
> diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
> index 319d68c..4222feb 100644
> --- a/drivers/tty/n_tty.c
> +++ b/drivers/tty/n_tty.c
> @@ -87,6 +87,10 @@
> # define n_tty_trace(f, args...) no_printk(f, ##args)
> #endif
>
> +#ifdef CONFIG_TTY_CONSOLE_STABLE
> +# define SIXTY_SEC_TIMEOUT (60 * HZ)
> +#endif
> +
> struct n_tty_data {
> /* producer-published */
> size_t read_head;
> @@ -2375,7 +2379,22 @@ static ssize_t n_tty_write(struct tty_struct *tty,
> struct file *file,
> }
> up_read(&tty->termios_rwsem);
>
> +#ifdef CONFIG_TTY_CONSOLE_STABLE
No #ifdefs in .c code.
> + /* Resolve the problem of loopback waiting when the serial port
> is damaged */
> + if (strncmp(tty->name, "ttyS", 4) == 0 || strncmp(tty->name,
> "ttyAMA", 6) == 0) {
Doing things based on a string is ripe for major problems.
greg k-h
