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:
> > On Wed, 13 Feb 2008 16:14:04 -0800
> > "Paul E. McKenney" <[EMAIL PROTECTED]> wrote:
> > > On Wed, Feb 13, 2008 at 03:51:58PM -0800, Stephen Hemminger wrote:
>
> [ . . . ]
>
> > > > Maybe cast both sides to void * in this case:
> > > >
> > > > static inline void node_set_parent(struct node *node, struct tnode *ptr)
> > > > {
> > > > rcu_assign_pointer((void *) node->parent, (void *)((unsigned
> > > > long)ptr | NODE_TYPE(node)));
> > > > }
> > >
> > > That gets me the following:
> > >
> > > net/ipv4/fib_trie.c: In function ‘node_set_parent’:
> > > net/ipv4/fib_trie.c:182: error: invalid lvalue in assignment
> > >
> > > However, as with much in computing, an extra level of indirection fixes
> > > things. Your call as to whether or not the cure is preferable to the
> > > disease. ;-)
> > >
> > > Signed-off-by: Paul E. McKenney <[EMAIL PROTECTED]>
> > > ---
> > >
> > > fib_trie.c | 4 ++--
> > > 1 file changed, 2 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 16:10:07.000000000 -0800
> > > @@ -179,8 +179,8 @@ 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_pointer((*(void **)&node->parent),
> > > + (void *)((unsigned long)ptr | NODE_TYPE(node)));
> > > }
> >
> > 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.
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