Re: [PATCH 1/1] tty: serial: samsung: add spin_lock for interrupt and console_write

Greg Kroah-Hartman
2022-04-05T05:03:24Z

On Tue, Apr 05, 2022 at 12:38:54PM +0900, Jaewon Kim wrote:
> The console_write and IRQ handler can run concurrently.
> Problems may occurs console_write is continuously executed while
> the IRQ handler is running.
>
> Signed-off-by: Jaewon Kim <jaewon02.kim@samsung.com>
> ---
> drivers/tty/serial/samsung_tty.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)

What commit does this fix?

>
> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> index e1585fbae909..d362e8e114f1 100644
> --- a/drivers/tty/serial/samsung_tty.c
> +++ b/drivers/tty/serial/samsung_tty.c
> @@ -2480,12 +2480,26 @@ s3c24xx_serial_console_write(struct console *co, const char *s,
> unsigned int count)
> {
> unsigned int ucon = rd_regl(cons_uart, S3C2410_UCON);
> + unsigned long flags;
> + int locked = 1;

bool?

>
> /* not possible to xmit on unconfigured port */
> if (!s3c24xx_port_configured(ucon))
> return;
>
> + local_irq_save(flags);
> + if (cons_uart->sysrq)
> + locked = 0;
> + else if (oops_in_progress)
> + locked = spin_trylock(&cons_uart->lock);
> + else
> + spin_lock(&cons_uart->lock);
> +
> uart_console_write(cons_uart, s, count, s3c24xx_serial_console_putchar);
> +
> + if (locked)
> + spin_unlock(&cons_uart->lock);
> + local_irq_restore(flags);

Why is irq_save required as well as a spinlock?

thanks,

greg k-h