linux-kernel - Re: [PATCH RESEND tty-next] serial: 8250_dw: Take port lock while accessing LSR

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Date:   Tue, 28 Jun 2022 13:56:59 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        linux-serial <linux-serial@...r.kernel.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND tty-next] serial: 8250_dw: Take port lock while
 accessing LSR

On Tue, Jun 28, 2022 at 12:01:28PM +0300, Ilpo Järvinen wrote:
> Accessing LSR requires port lock because it mutates lsr_saved_flags
> in serial_lsr_in().

Don't remember if I given or not (and why if not) the tag, so here it is:
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

> Fixes: 197eb5c416ff ("serial: 8250_dw: Use serial_lsr_in() in dw8250_handle_irq()")
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> 
> ---
> I'll resend the third patch later.
> 
>  drivers/tty/serial/8250/8250_dw.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
> index 167a691c7b19..f78b13db1b1e 100644
> --- a/drivers/tty/serial/8250/8250_dw.c
> +++ b/drivers/tty/serial/8250/8250_dw.c
> @@ -266,7 +266,10 @@ static int dw8250_handle_irq(struct uart_port *p)
>  
>  	/* Manually stop the Rx DMA transfer when acting as flow controller */
>  	if (quirks & DW_UART_QUIRK_IS_DMA_FC && up->dma && up->dma->rx_running && rx_timeout) {
> +		spin_lock_irqsave(&p->lock, flags);
>  		status = serial_lsr_in(up);
> +		spin_unlock_irqrestore(&p->lock, flags);
> +
>  		if (status & (UART_LSR_DR | UART_LSR_BI)) {
>  			dw8250_writel_ext(p, RZN1_UART_RDMACR, 0);
>  			dw8250_writel_ext(p, DW_UART_DMASA, 1);
> 
> -- 
> tg: (f55d2e4b0a47..) dw/use-spinlock (depends on: 8250/fix-stop_tx-race)


-- 
With Best Regards,
Andy Shevchenko