Subject: Re: [PATCH -rt] Fix initialization of spinlock in irttp_dup()

From: Samuel Ortiz <[email-masked]>
Date: Tue, 20 Mar 2007 23:50:12 +0200

Hi Deepak,

On Tue, Mar 20, 2007 at 12:22:33PM -0700, Deepak Saxena wrote:
> This was found around the 2.6.10 timeframe when testing with the -rt patch
> and I believe is still is an issue. irttp_dup() does a memcpy() of the tsap_cb 
> structure causing the spinlock protecting various fields in the structure to be 
> duped.  This works OK in the non-RT case but in the RT case we end up with two 
> mutexes pointing to the same wait_list and leading to an OOPS. Fix is to simply
> initialize the spinlock after the memcpy().
This has just made it to the netdev and stable trees.
See:
http://git.kernel.org/?p=linux/kernel/git/davem/net-2.6.git;a=commit;h=7bb1bbe615de25d955b974cb47d40fa198154bb9

Cheers,
Samuel.

> Signed-off-by: Deepak Saxena <[email-masked]>
> 
> diff --git a/net/irda/irttp.c b/net/irda/irttp.c
> index a7486b3..df2b2f7 100644
> --- a/net/irda/irttp.c
> +++ b/net/irda/irttp.c
> @@ -1441,6 +1441,7 @@ struct tsap_cb *irttp_dup(struct tsap_cb
>  	}
>  	/* Dup */
>  	memcpy(new, orig, sizeof(struct tsap_cb));
> +	spin_lock_init(&new->lock);
>  
>  	/* We don't need the old instance any more */
>  	spin_unlock_irqrestore(&irttp->tsaps->hb_spinlock, flags);
> 
> 
> -- 
> Deepak Saxena - [email-masked] - http://www.plexity.net
> 
> In the end, they will not say, "those were dark times,"  they will ask
> "why were their poets silent?" - Bertolt Brecht