linux-kernel - Re: [PATCH 3.10 219/268] tty/serial: atmel: fix race condition (TX+DMA)

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Date:   Tue, 20 Jun 2017 09:04:03 +0200
From:   Richard Genoud <richard.genoud@...il.com>
To:     Willy Tarreau <w@....eu>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "#4 . 4+" <stable@...r.kernel.org>, linux@...ck-us.net,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 3.10 219/268] tty/serial: atmel: fix race condition (TX+DMA)

Hi Willy,

You can drop this patch.

There's nothing to fix on 3.10.x since the DMA TX support has been
introduced in 3.12.

Thanks !


2017-06-19 20:31 GMT+02:00 Willy Tarreau <w@....eu>:
> From: Richard Genoud <richard.genoud@...il.com>
>
> commit 31ca2c63fdc0aee725cbd4f207c1256f5deaabde upstream.
>
> If uart_flush_buffer() is called between atmel_tx_dma() and
> atmel_complete_tx_dma(), the circular buffer has been cleared, but not
> atmel_port->tx_len.
> That leads to a circular buffer overflow (dumping (UART_XMIT_SIZE -
> atmel_port->tx_len) bytes).
>
> Tested-by: Nicolas Ferre <nicolas.ferre@...rochip.com>
> [rg] backport to 3.12
> Signed-off-by: Richard Genoud <richard.genoud@...il.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Signed-off-by: Willy Tarreau <w@....eu>
> ---
>  drivers/tty/serial/atmel_serial.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index 82127ac..41d1df5 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -1090,6 +1090,11 @@ static void atmel_flush_buffer(struct uart_port *port)
>                 UART_PUT_TCR(port, 0);
>                 atmel_port->pdc_tx.ofs = 0;
>         }
> +       /*
> +        * in uart_flush_buffer(), the xmit circular buffer has just
> +        * been cleared, so we have to reset its length accordingly.
> +        */
> +       sg_dma_len(&atmel_port->sg_tx) = 0;
>  }
>
>  /*
> --
> 2.8.0.rc2.1.gbe9624a
>