On Wed, 13 Feb 2008 17:34:27 -0800
"Paul E. McKenney" <[EMAIL PROTECTED]> wrote:
> On Wed, Feb 13, 2008 at 04:53:56PM -0800, Stephen Hemminger wrote:
> > On Wed, 13 Feb 2008 16:42:53 -0800
> > "Paul E. McKenney" <[EMAIL PROTECTED]> wrote:
> > > On Wed, Feb 13, 2008 at 04:27:00PM -0800, Stephen Hemminger wrote:
>
> [ . . . ]
>
> > > > That is heading towards ugly... Maybe not using the macro at all (for
> > > > this case) would be best:
> > > >
> > > > static inline void node_set_parent(struct node *node, struct tnode *ptr)
> > > > {
> > > > smp_wmb();
> > > > node->parent = (unsigned long)ptr | NODE_TYPE(node);
> > > > }
> > >
> > > Or, alternatively, the rcu_assign_index() patch sent earlier to avoid
> > > the bare memory barrier?
> > >
> > > Thanx, Paul
> >
> > I am fine with rcu_assign_index(), and add a comment in node_set_parent.
>
> OK, how about the following?
>
> Signed-off-by: Paul E. McKenney <[EMAIL PROTECTED]>
> ---
>
> fib_trie.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff -urpNa -X dontdiff linux-2.6.25-rc1/net/ipv4/fib_trie.c
> linux-2.6.25-rc1-fib_trie-warn.compile/net/ipv4/fib_trie.c
> --- linux-2.6.25-rc1/net/ipv4/fib_trie.c 2008-02-13 14:38:12.000000000
> -0800
> +++ linux-2.6.25-rc1-fib_trie-warn.compile/net/ipv4/fib_trie.c
> 2008-02-13 17:31:16.000000000 -0800
> @@ -96,6 +96,14 @@ typedef unsigned int t_key;
> #define IS_TNODE(n) (!(n->parent & T_LEAF))
> #define IS_LEAF(n) (n->parent & T_LEAF)
>
> +/*
> + * The "parent" fields in struct node and struct leaf are really pointers,
> + * but with the possibility that the T_LEAF bit is set. Therefore, both
> + * the C compiler and RCU see them as integers rather than pointers.
> + * This in turn means that rcu_assign_index() must be used to assign
> + * values to these fields, rather than the usual rcu_assign_pointer().
> + */
> +
> struct node {
> unsigned long parent;
> t_key key;
> @@ -179,8 +187,7 @@ static inline struct tnode *node_parent_
>
> static inline void node_set_parent(struct node *node, struct tnode *ptr)
> {
> - rcu_assign_pointer(node->parent,
> - (unsigned long)ptr | NODE_TYPE(node));
> + rcu_assign_index(node->parent, (unsigned long)ptr | NODE_TYPE(node));
> }
>
> static inline struct node *tnode_get_child(struct tnode *tn, unsigned int i)
Yes, thats great.
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