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

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Message-ID: <CAD=FV=WSKaihdow4Bbr6SSuUXL3s1u3it-=0Gkh95q=bwZuqnA@mail.gmail.com>
Date:   Thu, 25 May 2023 13:38:37 -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 9:07 AM Doug Anderson <dianders@...omium.org> wrote:
>
> 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?

Ah, I see. You did that in a separate patch and I wasn't CCed. I guess
I would have just put the two in one patch, but I don't feel that
strongly.

Reviewed-by: Douglas Anderson <dianders@...omium.org>