linux-kernel - Re: [PATCH tty v1 4/8] serial: core: lock port for start_rx() in uart_resume

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Date:   Thu, 25 May 2023 09:07:22 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Petr Mladek <pmladek@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, Jiri Slaby <jirislaby@...nel.org>,
        Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH tty v1 4/8] serial: core: lock port for start_rx() in uart_resume_port()

Hi,

On Thu, May 25, 2023 at 2:34 AM John Ogness <john.ogness@...utronix.de> wrote:
>
> The only user of the start_rx() callback (qcom_geni) directly calls
> its own stop_rx() callback. Since stop_rx() requires that the
> port->lock is taken and interrupts are disabled, the start_rx()
> callback has the same requirement.
>
> Fixes: cfab87c2c271 ("serial: core: Introduce callback for start_rx and do stop_rx in suspend only if this callback implementation is present.")
> Signed-off-by: John Ogness <john.ogness@...utronix.de>
> ---
>  drivers/tty/serial/serial_core.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index 37ad53616372..f856c7fae2fd 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -2430,8 +2430,11 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
>                 if (console_suspend_enabled)
>                         uart_change_pm(state, UART_PM_STATE_ON);
>                 uport->ops->set_termios(uport, &termios, NULL);
> -               if (!console_suspend_enabled && uport->ops->start_rx)
> +               if (!console_suspend_enabled && uport->ops->start_rx) {
> +                       spin_lock_irq(&uport->lock);
>                         uport->ops->start_rx(uport);
> +                       spin_unlock_irq(&uport->lock);
> +               }

Seems right, but shouldn't you also fix the call to stop_rx() that the
same commit cfab87c2c271 ("serial: core: Introduce callback for
start_rx and do stop_rx in suspend only if this callback
implementation is present.") added? That one is also missing the lock,
right?

-Doug