Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261295AbUJWUrq (ORCPT ); Sat, 23 Oct 2004 16:47:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261278AbUJWUrp (ORCPT ); Sat, 23 Oct 2004 16:47:45 -0400 Received: from pixpat.austin.ibm.com ([192.35.232.241]:50829 "EHLO linux.local") by vger.kernel.org with ESMTP id S261308AbUJWUop (ORCPT ); Sat, 23 Oct 2004 16:44:45 -0400 Date: Sat, 23 Oct 2004 13:39:39 -0700 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: akpm@osdl.org, dipankar@in.ibm.com, spraul@dbl.q-ag.de, rusty@au1.ibm.com, shemminger@osdl.org Subject: [PATCH 2/3] RCU: rcu_assign_pointer() removal of memory barriers Message-ID: <20041023203939.GA4738@us.ibm.com> Reply-To: paulmck@us.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5254 Lines: 141 This patch uses the rcu_assign_pointer() API to eliminate a number of explicit memory barriers from code using RCU. This has been tested successfully on i386 and ppc64. Signed-off-by: --- arch/x86_64/kernel/mce.c | 3 +-- include/linux/list.h | 2 -- net/core/netfilter.c | 3 +-- net/decnet/dn_route.c | 13 +++++-------- net/ipv4/devinet.c | 3 +-- net/ipv4/route.c | 7 +++---- net/sched/sch_api.c | 3 +-- 7 files changed, 12 insertions(+), 22 deletions(-) diff -urpN -X ../dontdiff linux-2.5/arch/x86_64/kernel/mce.c linux-2.5-rap/arch/x86_64/kernel/mce.c --- linux-2.5/arch/x86_64/kernel/mce.c Tue Sep 7 10:02:15 2004 +++ linux-2.5-rap/arch/x86_64/kernel/mce.c Tue Sep 7 10:29:18 2004 @@ -358,8 +358,7 @@ static ssize_t mce_read(struct file *fil memset(mcelog.entry, 0, next * sizeof(struct mce)); mcelog.next = 0; - smp_wmb(); - + synchronize_kernel(); /* Collect entries that were still getting written before the synchronize. */ diff -urpN -X ../dontdiff linux-2.5/include/linux/list.h linux-2.5-rap/include/linux/list.h --- linux-2.5/include/linux/list.h Tue Sep 7 10:04:28 2004 +++ linux-2.5-rap/include/linux/list.h Tue Sep 7 10:42:56 2004 @@ -553,8 +553,6 @@ static inline void hlist_del_init(struct } } -#define hlist_del_rcu_init hlist_del_init - static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h) { struct hlist_node *first = h->first; diff -urpN -X ../dontdiff linux-2.5/net/core/netfilter.c linux-2.5-rap/net/core/netfilter.c --- linux-2.5/net/core/netfilter.c Tue Sep 7 10:04:41 2004 +++ linux-2.5-rap/net/core/netfilter.c Tue Sep 7 10:29:20 2004 @@ -751,10 +751,9 @@ int nf_log_register(int pf, nf_logfn *lo /* Any setup of logging members must be done before * substituting pointer. */ - smp_wmb(); spin_lock(&nf_log_lock); if (!nf_logging[pf]) { - nf_logging[pf] = logfn; + rcu_assign_pointer(nf_logging[pf], logfn); ret = 0; } spin_unlock(&nf_log_lock); diff -urpN -X ../dontdiff linux-2.5/net/decnet/dn_route.c linux-2.5-rap/net/decnet/dn_route.c --- linux-2.5/net/decnet/dn_route.c Tue Sep 7 10:04:41 2004 +++ linux-2.5-rap/net/decnet/dn_route.c Tue Sep 7 10:29:24 2004 @@ -287,10 +287,9 @@ static int dn_insert_route(struct dn_rou if (compare_keys(&rth->fl, &rt->fl)) { /* Put it first */ *rthp = rth->u.rt_next; - smp_wmb(); - rth->u.rt_next = dn_rt_hash_table[hash].chain; - smp_wmb(); - dn_rt_hash_table[hash].chain = rth; + rcu_assign_pointer(rth->u.rt_next, + dn_rt_hash_table[hash].chain); + rcu_assign_pointer(dn_rt_hash_table[hash].chain, rth); rth->u.dst.__use++; dst_hold(&rth->u.dst); @@ -304,10 +303,8 @@ static int dn_insert_route(struct dn_rou rthp = &rth->u.rt_next; } - smp_wmb(); - rt->u.rt_next = dn_rt_hash_table[hash].chain; - smp_wmb(); - dn_rt_hash_table[hash].chain = rt; + rcu_assign_pointer(rt->u.rt_next, dn_rt_hash_table[hash].chain); + rcu_assign_pointer(dn_rt_hash_table[hash].chain, rt); dst_hold(&rt->u.dst); rt->u.dst.__use++; diff -urpN -X ../dontdiff linux-2.5/net/ipv4/devinet.c linux-2.5-rap/net/ipv4/devinet.c --- linux-2.5/net/ipv4/devinet.c Tue Sep 7 10:04:42 2004 +++ linux-2.5-rap/net/ipv4/devinet.c Tue Sep 7 10:29:25 2004 @@ -158,8 +158,7 @@ struct in_device *inetdev_init(struct ne /* Account for reference dev->ip_ptr */ in_dev_hold(in_dev); - smp_wmb(); - dev->ip_ptr = in_dev; + rcu_assign_pointer(dev->ip_ptr, in_dev); #ifdef CONFIG_SYSCTL devinet_sysctl_register(in_dev, &in_dev->cnf); diff -urpN -X ../dontdiff linux-2.5/net/ipv4/route.c linux-2.5-rap/net/ipv4/route.c --- linux-2.5/net/ipv4/route.c Tue Sep 7 10:04:42 2004 +++ linux-2.5-rap/net/ipv4/route.c Tue Sep 7 10:29:27 2004 @@ -793,14 +793,13 @@ restart: * must be visible to another weakly ordered CPU before * the insertion at the start of the hash chain. */ - smp_wmb(); - rth->u.rt_next = rt_hash_table[hash].chain; + rcu_assign_pointer(rth->u.rt_next, + rt_hash_table[hash].chain); /* * Since lookup is lockfree, the update writes * must be ordered for consistency on SMP. */ - smp_wmb(); - rt_hash_table[hash].chain = rth; + rcu_assign_pointer(rt_hash_table[hash].chain, rth); rth->u.dst.__use++; dst_hold(&rth->u.dst); diff -urpN -X ../dontdiff linux-2.5/net/sched/sch_api.c linux-2.5-rap/net/sched/sch_api.c --- linux-2.5/net/sched/sch_api.c Tue Sep 7 10:04:46 2004 +++ linux-2.5-rap/net/sched/sch_api.c Tue Sep 7 10:29:28 2004 @@ -451,10 +451,9 @@ qdisc_create(struct net_device *dev, u32 /* enqueue is accessed locklessly - make sure it's visible * before we set a netdevice's qdisc pointer to sch */ - smp_wmb(); if (!ops->init || (err = ops->init(sch, tca[TCA_OPTIONS-1])) == 0) { qdisc_lock_tree(dev); - list_add_tail(&sch->list, &dev->qdisc_list); + list_add_tail_rcu(&sch->list, &dev->qdisc_list); qdisc_unlock_tree(dev); #ifdef CONFIG_NET_ESTIMATOR - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/