Re: Patch "serial: 8250_dw: Fix deadlock in LCR workaround" has been added to the 3.19-stable tree

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Hi Greg,

The 3.10-stable tree needs this patch too.
Can you push this patch to 3.10 stable tree ?

Best regards!

On 2015/3/24 18:35, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
> 
> This is a note to let you know that I've just added the patch titled
> 
>     serial: 8250_dw: Fix deadlock in LCR workaround
> 
> to the 3.19-stable tree which can be found at:
>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> 
> The filename of the patch is:
>      serial-8250_dw-fix-deadlock-in-lcr-workaround.patch
> and it can be found in the queue-3.19 subdirectory.
> 
> If you, or anyone else, feels it should not be added to the stable tree,
> please let <stable@xxxxxxxxxxxxxxx> know about it.
> 
> 
>>From 7fd6f640f2dd17dac6ddd6702c378cb0bb9cfa11 Mon Sep 17 00:00:00 2001
> From: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
> Date: Wed, 11 Mar 2015 09:19:16 -0400
> Subject: serial: 8250_dw: Fix deadlock in LCR workaround
> 
> From: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
> 
> commit 7fd6f640f2dd17dac6ddd6702c378cb0bb9cfa11 upstream.
> 
> Trying to write console output from within the serial console driver
> while the port->lock is held causes recursive deadlock:
> 
>   CPU 0
> spin_lock_irqsave(&port->lock)
> printk()
>   console_unlock()
>     call_console_drivers()
>       serial8250_console_write()
>         spin_lock_irqsave(&port->lock)
> ** DEADLOCK **
> 
> The 8250_dw i/o accessors try to write a console error message if the
> LCR workaround was unsuccessful. When the port->lock is already held
> (eg., when called from serial8250_set_termios()), this deadlocks.
> 
> Make the error message a FIXME until a general solution is devised.
> 
> Cc: Tim Kryger <tim.kryger@xxxxxxxxx>
> Reported-by: Zhang Zhen <zhenzhang.zhang@xxxxxxxxxx>
> Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> 
> ---
>  drivers/tty/serial/8250/8250_dw.c |   15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> --- a/drivers/tty/serial/8250/8250_dw.c
> +++ b/drivers/tty/serial/8250/8250_dw.c
> @@ -111,7 +111,10 @@ static void dw8250_serial_out(struct uar
>  			dw8250_force_idle(p);
>  			writeb(value, p->membase + (UART_LCR << p->regshift));
>  		}
> -		dev_err(p->dev, "Couldn't set LCR to %d\n", value);
> +		/*
> +		 * FIXME: this deadlocks if port->lock is already held
> +		 * dev_err(p->dev, "Couldn't set LCR to %d\n", value);
> +		 */
>  	}
>  }
>  
> @@ -155,7 +158,10 @@ static void dw8250_serial_outq(struct ua
>  			__raw_writeq(value & 0xff,
>  				     p->membase + (UART_LCR << p->regshift));
>  		}
> -		dev_err(p->dev, "Couldn't set LCR to %d\n", value);
> +		/*
> +		 * FIXME: this deadlocks if port->lock is already held
> +		 * dev_err(p->dev, "Couldn't set LCR to %d\n", value);
> +		 */
>  	}
>  }
>  #endif /* CONFIG_64BIT */
> @@ -179,7 +185,10 @@ static void dw8250_serial_out32(struct u
>  			dw8250_force_idle(p);
>  			writel(value, p->membase + (UART_LCR << p->regshift));
>  		}
> -		dev_err(p->dev, "Couldn't set LCR to %d\n", value);
> +		/*
> +		 * FIXME: this deadlocks if port->lock is already held
> +		 * dev_err(p->dev, "Couldn't set LCR to %d\n", value);
> +		 */
>  	}
>  }
>  
> 
> 
> Patches currently in stable-queue which might be from peter@xxxxxxxxxxxxxxxxxx are
> 
> queue-3.19/serial-core-fix-iotype-userspace-breakage.patch
> queue-3.19/console-fix-console-name-size-mismatch.patch
> queue-3.19/serial-8250_dw-fix-deadlock-in-lcr-workaround.patch
> 
> .
> 


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