* Peter Zijlstra <peterz@xxxxxxxxxxxxx> [2011-09-26 13:18:40]:
> On Tue, 2011-09-20 at 17:29 +0530, Srikar Dronamraju wrote:
> > +static struct uprobe *__insert_uprobe(struct uprobe *uprobe)
> > +{
> > + struct rb_node **p = &uprobes_tree.rb_node;
> > + struct rb_node *parent = NULL;
> > + struct uprobe *u;
> > + int match;
> > +
> > + while (*p) {
> > + parent = *p;
> > + u = rb_entry(parent, struct uprobe, rb_node);
> > + match = match_uprobe(uprobe, u);
> > + if (!match) {
> > + atomic_inc(&u->ref);
> > + return u;
> > + }
> > +
> > + if (match < 0)
> > + p = &parent->rb_left;
> > + else
> > + p = &parent->rb_right;
> > +
> > + }
> > + u = NULL;
> > + rb_link_node(&uprobe->rb_node, parent, p);
> > + rb_insert_color(&uprobe->rb_node, &uprobes_tree);
> > + /* get access + drop ref */
> > + atomic_set(&uprobe->ref, 2);
> > + return u;
> > +}
>
> If you ever want to make a 'lockless' lookup work you need to set the
> refcount of the new object before its fully visible, instead of after.
>
Agree,
> Now much of a problem now since its fully serialized by that
> uprobes_treelock thing.
>
Will stick with this for now; If and when we do a lockless lookup we
could fix this.
--
Thanks and Regards
Srikar
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