Re: [PATCH] Fix cpm uart corruption with PREEMPT_RT

[Scott Wood]

On Tue, May 20, 2008 at 02:28:16PM -0500, Rune Torgersen wrote:
> Fix CPM serial port corruption when running with CONFIG_PREEMPT_RT.
> Userland usage of console, and kernel printf's were stepping on each others 
> toes.
> 
> Signed-off-by: Rune Torgersen <[EMAIL PROTECTED]>
> 
> diff --git a/drivers/serial/cpm_uart/cpm_uart_core.c 
> b/drivers/serial/cpm_uart/cpm_uart_core.c
> index fb93403..79c109d 100755
> --- a/drivers/serial/cpm_uart/cpm_uart_core.c
> +++ b/drivers/serial/cpm_uart/cpm_uart_core.c
> @@ -1214,7 +1214,9 @@ static void cpm_uart_console_write(struct console *co, 
> const char *s,
>       unsigned int i;
>       cbd_t __iomem *bdp, *bdbase;
>       unsigned char *cp;
> +     unsigned long flags;
>  
> +     spin_lock_irqsave(&pinfo->port.lock, flags);
>       /* Get the address of the host memory buffer.
>        */
>       bdp = pinfo->tx_cur;
> @@ -1282,6 +1284,8 @@ static void cpm_uart_console_write(struct console *co, 
> const char *s,
>               ;
>  
>       pinfo->tx_cur = bdp;
> +
> +     spin_unlock_irqrestore(&pinfo->port.lock, flags);
>  }

We should bypass the lock when oops_in_progress is set, something like:

diff --git a/drivers/serial/cpm_uart/cpm_uart_core.c 
b/drivers/serial/cpm_uart/cpm_uart_core.c
index a19dc7e..bc45f8a 100644
--- a/drivers/serial/cpm_uart/cpm_uart_core.c
+++ b/drivers/serial/cpm_uart/cpm_uart_core.c
@@ -1178,6 +1178,14 @@ static void cpm_uart_console_write(struct console *co, 
const char *s,
        unsigned int i;
        cbd_t __iomem *bdp, *bdbase;
        unsigned char *cp;
+       unsigned long flags;
+       int nolock = oops_in_progress;
+
+       if (unlikely(nolock)) {
+               local_irq_save(flags);
+       } else {
+               spin_lock_irqsave(&pinfo->port.lock, flags);
+       }
 
        /* Get the address of the host memory buffer.
         */
@@ -1239,8 +1247,13 @@ static void cpm_uart_console_write(struct console *co, 
const char *s,
                ;
 
        pinfo->tx_cur = bdp;
-}
 
+       if (unlikely(nolock)) {
+               local_irq_restore(flags);
+       } else {
+               spin_unlock_irqrestore(&pinfo->port.lock, flags);
+       }
+}
 
 static int __init cpm_uart_console_setup(struct console *co, char *options)
 {

-Scott
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