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SubjectRe: [PATCH 1/2] tty: serial: imx: add lock for registers save/restore
Hello,

On Thu, Aug 09, 2018 at 06:06:08PM +0800, Anson Huang wrote:
> In noirq suspend/resume stage with no_console_suspend enabled,
> .imx_console_write() may be called to print out log_buf
> message by .printk(), so there will be race condition between
> .imx_console_write() and .serial_imx_save/restore_context(),
> need to add lock to protect the registers save/restore operations.

The function names changes some time ago. Also I'd drop the leading dots
in the names which I would understand as members in a struct.

Is this a theoretical issue, or did you see actual breakage?

> Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
> ---
> drivers/tty/serial/imx.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 239c0fa..a09ccef 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -2376,9 +2376,12 @@ static int imx_uart_remove(struct platform_device *pdev)
>
> static void imx_uart_restore_context(struct imx_port *sport)
> {
> + unsigned long flags;
> +
> if (!sport->context_saved)
> return;

Is it safe to check .context_saved without holding the lock?

> + spin_lock_irqsave(&sport->port.lock, flags);
> imx_uart_writel(sport, sport->saved_reg[4], UFCR);
> imx_uart_writel(sport, sport->saved_reg[5], UESC);
> imx_uart_writel(sport, sport->saved_reg[6], UTIM);
> @@ -2390,11 +2393,15 @@ static void imx_uart_restore_context(struct imx_port *sport)
> imx_uart_writel(sport, sport->saved_reg[2], UCR3);
> imx_uart_writel(sport, sport->saved_reg[3], UCR4);
> sport->context_saved = false;
> + spin_unlock_irqrestore(&sport->port.lock, flags);
> }
>
> static void imx_uart_save_context(struct imx_port *sport)
> {
> + unsigned long flags;
> +
> /* Save necessary regs */
> + spin_lock_irqsave(&sport->port.lock, flags);
> sport->saved_reg[0] = imx_uart_readl(sport, UCR1);
> sport->saved_reg[1] = imx_uart_readl(sport, UCR2);
> sport->saved_reg[2] = imx_uart_readl(sport, UCR3);
> @@ -2406,6 +2413,7 @@ static void imx_uart_save_context(struct imx_port *sport)
> sport->saved_reg[8] = imx_uart_readl(sport, UBMR);
> sport->saved_reg[9] = imx_uart_readl(sport, IMX21_UTS);
> sport->context_saved = true;
> + spin_unlock_irqrestore(&sport->port.lock, flags);
> }
>
> static void imx_uart_enable_wakeup(struct imx_port *sport, bool on)

Best regards
Uwe

--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |

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