From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: [PATCH RFC tip/core/rcu 14/15] netfilter: Remove now-redundant smp_read_barrier_depends() Date: Mon, 9 Oct 2017 17:22:48 -0700 Message-ID: <1507594969-8347-14-git-send-email-paulmck@linux.vnet.ibm.com> References: <20171010001951.GA6476@linux.vnet.ibm.com> Return-path: In-Reply-To: <20171010001951.GA6476@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, torvalds@linux-foundation.org, mark.rutland@arm.com, dhowells@redhat.com, linux-arch@vger.kernel.org, peterz@infradead.org, will.deacon@arm.com, "Paul E. McKenney" , Pablo Neira Ayuso , Jozsef Kadlecsik , Florian Westphal , "David S. Miller" , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org List-Id: linux-arch.vger.kernel.org READ_ONCE() now implies smp_read_barrier_depends(), which means that the instances in arpt_do_table(), ipt_do_table(), and ip6t_do_table() are now redundant. This commit removes them and adjusts the comments. Signed-off-by: Paul E. McKenney Cc: Pablo Neira Ayuso Cc: Jozsef Kadlecsik Cc: Florian Westphal Cc: "David S. Miller" Cc: Cc: Cc: --- net/ipv4/netfilter/arp_tables.c | 7 +------ net/ipv4/netfilter/ip_tables.c | 7 +------ net/ipv6/netfilter/ip6_tables.c | 7 +------ 3 files changed, 3 insertions(+), 18 deletions(-) diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c index 9e2770fd00be..d555b3b31c49 100644 --- a/net/ipv4/netfilter/arp_tables.c +++ b/net/ipv4/netfilter/arp_tables.c @@ -202,13 +202,8 @@ unsigned int arpt_do_table(struct sk_buff *skb, local_bh_disable(); addend = xt_write_recseq_begin(); - private = table->private; + private = READ_ONCE(table->private); /* Address dependency. */ cpu = smp_processor_id(); - /* - * Ensure we load private-> members after we've fetched the base - * pointer. - */ - smp_read_barrier_depends(); table_base = private->entries; jumpstack = (struct arpt_entry **)private->jumpstack[cpu]; diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c index 39286e543ee6..f63752bec442 100644 --- a/net/ipv4/netfilter/ip_tables.c +++ b/net/ipv4/netfilter/ip_tables.c @@ -260,13 +260,8 @@ ipt_do_table(struct sk_buff *skb, WARN_ON(!(table->valid_hooks & (1 << hook))); local_bh_disable(); addend = xt_write_recseq_begin(); - private = table->private; + private = READ_ONCE(table->private); /* Address dependency. */ cpu = smp_processor_id(); - /* - * Ensure we load private-> members after we've fetched the base - * pointer. - */ - smp_read_barrier_depends(); table_base = private->entries; jumpstack = (struct ipt_entry **)private->jumpstack[cpu]; diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c index 01bd3ee5ebc6..52afcab9b0d6 100644 --- a/net/ipv6/netfilter/ip6_tables.c +++ b/net/ipv6/netfilter/ip6_tables.c @@ -282,12 +282,7 @@ ip6t_do_table(struct sk_buff *skb, local_bh_disable(); addend = xt_write_recseq_begin(); - private = table->private; - /* - * Ensure we load private-> members after we've fetched the base - * pointer. - */ - smp_read_barrier_depends(); + private = READ_ONCE(table->private); /* Address dependency. */ cpu = smp_processor_id(); table_base = private->entries; jumpstack = (struct ip6t_entry **)private->jumpstack[cpu]; -- 2.5.2 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:48274 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755849AbdJJAW5 (ORCPT ); Mon, 9 Oct 2017 20:22:57 -0400 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v9A0JPEh117927 for ; Mon, 9 Oct 2017 20:22:57 -0400 Received: from e15.ny.us.ibm.com (e15.ny.us.ibm.com [129.33.205.205]) by mx0b-001b2d01.pphosted.com with ESMTP id 2dgcabvs8b-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 09 Oct 2017 20:22:56 -0400 Received: from localhost by e15.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 9 Oct 2017 20:22:56 -0400 From: "Paul E. McKenney" Subject: [PATCH RFC tip/core/rcu 14/15] netfilter: Remove now-redundant smp_read_barrier_depends() Date: Mon, 9 Oct 2017 17:22:48 -0700 In-Reply-To: <20171010001951.GA6476@linux.vnet.ibm.com> References: <20171010001951.GA6476@linux.vnet.ibm.com> Message-ID: <1507594969-8347-14-git-send-email-paulmck@linux.vnet.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, torvalds@linux-foundation.org, mark.rutland@arm.com, dhowells@redhat.com, linux-arch@vger.kernel.org, peterz@infradead.org, will.deacon@arm.com, "Paul E. McKenney" , Pablo Neira Ayuso , Jozsef Kadlecsik , Florian Westphal , "David S. Miller" , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org Message-ID: <20171010002248.bGwEtrAX-8DDy6esLbObVWDdln09lHqXNoSa8zX5KIk@z> READ_ONCE() now implies smp_read_barrier_depends(), which means that the instances in arpt_do_table(), ipt_do_table(), and ip6t_do_table() are now redundant. This commit removes them and adjusts the comments. Signed-off-by: Paul E. McKenney Cc: Pablo Neira Ayuso Cc: Jozsef Kadlecsik Cc: Florian Westphal Cc: "David S. Miller" Cc: Cc: Cc: --- net/ipv4/netfilter/arp_tables.c | 7 +------ net/ipv4/netfilter/ip_tables.c | 7 +------ net/ipv6/netfilter/ip6_tables.c | 7 +------ 3 files changed, 3 insertions(+), 18 deletions(-) diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c index 9e2770fd00be..d555b3b31c49 100644 --- a/net/ipv4/netfilter/arp_tables.c +++ b/net/ipv4/netfilter/arp_tables.c @@ -202,13 +202,8 @@ unsigned int arpt_do_table(struct sk_buff *skb, local_bh_disable(); addend = xt_write_recseq_begin(); - private = table->private; + private = READ_ONCE(table->private); /* Address dependency. */ cpu = smp_processor_id(); - /* - * Ensure we load private-> members after we've fetched the base - * pointer. - */ - smp_read_barrier_depends(); table_base = private->entries; jumpstack = (struct arpt_entry **)private->jumpstack[cpu]; diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c index 39286e543ee6..f63752bec442 100644 --- a/net/ipv4/netfilter/ip_tables.c +++ b/net/ipv4/netfilter/ip_tables.c @@ -260,13 +260,8 @@ ipt_do_table(struct sk_buff *skb, WARN_ON(!(table->valid_hooks & (1 << hook))); local_bh_disable(); addend = xt_write_recseq_begin(); - private = table->private; + private = READ_ONCE(table->private); /* Address dependency. */ cpu = smp_processor_id(); - /* - * Ensure we load private-> members after we've fetched the base - * pointer. - */ - smp_read_barrier_depends(); table_base = private->entries; jumpstack = (struct ipt_entry **)private->jumpstack[cpu]; diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c index 01bd3ee5ebc6..52afcab9b0d6 100644 --- a/net/ipv6/netfilter/ip6_tables.c +++ b/net/ipv6/netfilter/ip6_tables.c @@ -282,12 +282,7 @@ ip6t_do_table(struct sk_buff *skb, local_bh_disable(); addend = xt_write_recseq_begin(); - private = table->private; - /* - * Ensure we load private-> members after we've fetched the base - * pointer. - */ - smp_read_barrier_depends(); + private = READ_ONCE(table->private); /* Address dependency. */ cpu = smp_processor_id(); table_base = private->entries; jumpstack = (struct ip6t_entry **)private->jumpstack[cpu]; -- 2.5.2