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

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Date:	Fri, 28 Sep 2007 11:26:34 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jeff Dike <jdike@...toit.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	uml-devel <user-mode-linux-devel@...ts.sourceforge.net>
Subject: Re: [PATCH] UML - Fix locking in skb alloction failure fix

On Fri, 28 Sep 2007 11:43:14 -0400 Jeff Dike <jdike@...toit.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@...ux.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??
-
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