netdev - Re: xfrm_state locking regression...

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Date:	Tue, 9 Sep 2008 10:18:28 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	David Miller <davem@...emloft.net>
Cc:	timo.teras@....fi, netdev@...r.kernel.org
Subject: Re: xfrm_state locking regression...

On Mon, Sep 08, 2008 at 05:09:07PM -0700, David Miller wrote:
> From: Herbert Xu <herbert@...dor.apana.org.au>
> Date: Fri, 5 Sep 2008 21:55:07 +1000
> 
> > @@ -403,17 +408,23 @@ static void xfrm_state_gc_destroy(struct xfrm_state *x)
> >  
> >  static void xfrm_state_gc_task(struct work_struct *data)
> >  {
> > -	struct xfrm_state *x;
> > -	struct hlist_node *entry, *tmp;
> > -	struct hlist_head gc_list;
> > +	struct xfrm_state *x, *tmp;
> > +	static LIST_HEAD(gc_list);
> > +	unsigned long completed;
> >  
> >  	spin_lock_bh(&xfrm_state_gc_lock);
> > -	gc_list.first = xfrm_state_gc_list.first;
> > -	INIT_HLIST_HEAD(&xfrm_state_gc_list);
> > +	list_splice_tail_init(&xfrm_state_gc_list, &gc_list);
> >  	spin_unlock_bh(&xfrm_state_gc_lock);
> >  
> > -	hlist_for_each_entry_safe(x, entry, tmp, &gc_list, bydst)
> > +	mutex_lock(&xfrm_cfg_mutex);
> > +	completed = xfrm_state_walk_completed;
> > +	mutex_unlock(&xfrm_cfg_mutex);
> > +
> > +	list_for_each_entry_safe(x, tmp, &gc_list, gclist) {
> > +		if ((long)(x->lastused - completed) > 0)
> > +			break;
> >  		xfrm_state_gc_destroy(x);
> > +	}
> >  
> >  	wake_up(&km_waitq);
> >  }
> 
> What happens to all of the entries on the local gc_list which you
> will be skipping when you break out of that last loop?
> 
> It looks like they will never get processed.

I made gc_list static, so they'll be processed when the GC task
runs again.  Also whenever completed is incremented we schedule
the GC task.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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