Messages in this thread | | | Date | Tue, 12 Feb 2008 18:35:21 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 3/4] fib_trie: print statistics for multiple tables |
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On Tue, 12 Feb 2008 16:50:45 -0800 Stephen Hemminger <shemminger@vyatta.com> wrote:
> +/** > + * hlist_for_each_entry_continue_rcu - iterate over rcu hlist after current point > + * @tpos: the type * to use as a loop cursor. > + * @pos: the &struct hlist_node to use as a loop cursor. > + * @member: the name of the hlist_node within the struct. > + */ > +#define hlist_for_each_entry_continue_rcu(tpos, pos, member) \ > + for (pos = (pos)->next; \ > + rcu_dereference(pos) && ({ prefetch(pos->next); 1;}) && \ > + ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \ > + pos = pos->next)
Is the compiler allowed to look at a term such as
({ prefetch(pos->next); 1;})
and, when it is used as a truth value, say "hey, that's always true" and then elide the call to prefetch()? We've no way of telling because this remains gcc-specific territory, afaik.
(cc Paul for rcu stuff)
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