lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Wed, 13 Feb 2008 14:26:27 -0800 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Stephen Hemminger <shemminger@...tta.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH 3/4] fib_trie: print statistics for multiple tables On Tue, Feb 12, 2008 at 06:35:21PM -0800, Andrew Morton wrote: > On Tue, 12 Feb 2008 16:50:45 -0800 Stephen Hemminger <shemminger@...tta.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. The prefetch() definitions I found are "asm volatile". So, as I understand it, the compiler is not supposed to remove it, just as it would not be permitted to remove something that could have a side effect. > (cc Paul for rcu stuff) Given my track record with simple functions of late :-/ I will beat this one up a bit... Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists