[PATCH] UML - Fix locking in skb alloction failure fix

[PATCH] UML - Fix locking in skb alloction failure fix

[Jeff Dike]

Add _irqsave/_irqrestore to the locking in update_drop_skb to keep
uml_net_rx out while the drop skb is being messed with.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
---
 arch/um/drivers/net_kern.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Index: linux-2.6.22/arch/um/drivers/net_kern.c
===================================================================
--- linux-2.6.22.orig/arch/um/drivers/net_kern.c	2007-09-28 11:10:19.000000000 -0400
+++ linux-2.6.22/arch/um/drivers/net_kern.c	2007-09-28 11:13:58.000000000 -0400
@@ -49,9 +49,10 @@ static int drop_max;
 static int update_drop_skb(int max)
 {
 	struct sk_buff *new;
+	unsigned long flags;
 	int err = 0;
 
-	spin_lock(&drop_lock);
+	spin_lock_irqsave(&drop_lock, flags);
 
 	if (max <= drop_max)
 		goto out;
@@ -68,7 +69,7 @@ static int update_drop_skb(int max)
 	drop_max = max;
 	err = 0;
 out:
-	spin_unlock(&drop_lock);
+	spin_unlock_irqrestore(&drop_lock, flags);
 
 	return err;
 }

Re: [PATCH] UML - Fix locking in skb alloction failure fix

[Andrew Morton]

On Fri, 28 Sep 2007 11:43:14 -0400 Jeff Dike <jdike@addtoit.com> wrote:

> Add _irqsave/_irqrestore to the locking in update_drop_skb to keep
> uml_net_rx out while the drop skb is being messed with.
> 
> Signed-off-by: Jeff Dike <jdike@linux.intel.com>
> ---
>  arch/um/drivers/net_kern.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> Index: linux-2.6.22/arch/um/drivers/net_kern.c
> ===================================================================
> --- linux-2.6.22.orig/arch/um/drivers/net_kern.c	2007-09-28 11:10:19.000000000 -0400
> +++ linux-2.6.22/arch/um/drivers/net_kern.c	2007-09-28 11:13:58.000000000 -0400
> @@ -49,9 +49,10 @@ static int drop_max;
>  static int update_drop_skb(int max)
>  {
>  	struct sk_buff *new;
> +	unsigned long flags;
>  	int err = 0;
>  
> -	spin_lock(&drop_lock);
> +	spin_lock_irqsave(&drop_lock, flags);
>  
>  	if (max <= drop_max)
>  		goto out;
> @@ -68,7 +69,7 @@ static int update_drop_skb(int max)
>  	drop_max = max;
>  	err = 0;
>  out:
> -	spin_unlock(&drop_lock);
> +	spin_unlock_irqrestore(&drop_lock, flags);
>  
>  	return err;
>  }

Doesn't this assume that the arch is only ever uniprocessor, which I don't think is
true on i386 UML??

Re: [PATCH] UML - Fix locking in skb alloction failure fix

[Jeff Dike]

On Fri, Sep 28, 2007 at 11:26:34AM -0700, Andrew Morton wrote:
> Doesn't this assume that the arch is only ever uniprocessor, which I
> don't think is true on i386 UML??

It is for now, and when that changes, I haven't decided if and when
interrupts will be received on multiple CPUs.

				Jeff

-- 
Work email - jdike at linux dot intel dot com