From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: [PATCH 07/19] net: netlink/netfilter: Kill off ACCESS_ONCE() Date: Mon, 23 Oct 2017 14:07:17 -0700 Message-ID: <1508792849-3115-7-git-send-email-paulmck@linux.vnet.ibm.com> References: <20171023210408.GA2930@linux.vnet.ibm.com> Return-path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:47562 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751617AbdJWVHm (ORCPT ); Mon, 23 Oct 2017 17:07:42 -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 v9NL7Jcc137693 for ; Mon, 23 Oct 2017 17:07:42 -0400 Received: from e19.ny.us.ibm.com (e19.ny.us.ibm.com [129.33.205.209]) by mx0b-001b2d01.pphosted.com with ESMTP id 2dsheuaqrk-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 23 Oct 2017 17:07:41 -0400 Received: from localhost by e19.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 23 Oct 2017 17:07:41 -0400 In-Reply-To: <20171023210408.GA2930@linux.vnet.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: mingo@kernel.org Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, will.deacon@arm.com, mark.rutland@arm.com, snitzer@redhat.com, thor.thayer@linux.intel.com, viro@zeniv.linux.org.uk, davem@davemloft.net, shuah@kernel.org, mpe@ellerman.id.au, tj@kernel.org, torvalds@linux-foundation.org, Florian Westphal , Jozsef Kadlecsik , Pablo Neira Ayuso From: Mark Rutland For several reasons, it is desirable to use {READ,WRITE}_ONCE() in preference to ACCESS_ONCE(), and new code is expected to use one of the former. So far, there's been no reason to change most existing uses of ACCESS_ONCE(), as these aren't currently harmful. However, for some features it is necessary to instrument reads and writes separately, which is not possible with ACCESS_ONCE(). This distinction is critical to correct operation. It's possible to transform the bulk of kernel code using the Coccinelle script below. However, this doesn't handle comments, leaving references to ACCESS_ONCE() instances which have been removed. As a preparatory step, this patch converts netlink and netfilter code and comments to use {READ,WRITE}_ONCE() consistently. ---- virtual patch @ depends on patch @ expression E1, E2; @@ - ACCESS_ONCE(E1) = E2 + WRITE_ONCE(E1, E2) @ depends on patch @ expression E; @@ - ACCESS_ONCE(E) + READ_ONCE(E) ---- Signed-off-by: Mark Rutland Cc: David S. Miller Cc: Florian Westphal Cc: Jozsef Kadlecsik Cc: Pablo Neira Ayuso --- include/linux/genetlink.h | 2 +- include/linux/netfilter/nfnetlink.h | 2 +- include/linux/rtnetlink.h | 2 +- include/net/netfilter/nf_tables.h | 4 ++-- net/netfilter/ipvs/ip_vs_sync.c | 2 +- net/netfilter/nfnetlink_queue.c | 4 ++-- 6 files changed, 8 insertions(+), 8 deletions(-) diff --git a/include/linux/genetlink.h b/include/linux/genetlink.h index a4c61cbce777..0e694cf62414 100644 --- a/include/linux/genetlink.h +++ b/include/linux/genetlink.h @@ -30,7 +30,7 @@ extern wait_queue_head_t genl_sk_destructing_waitq; * @p: The pointer to read, prior to dereferencing * * Return the value of the specified RCU-protected pointer, but omit - * both the smp_read_barrier_depends() and the ACCESS_ONCE(), because + * both the smp_read_barrier_depends() and the READ_ONCE(), because * caller holds genl mutex. */ #define genl_dereference(p) \ diff --git a/include/linux/netfilter/nfnetlink.h b/include/linux/netfilter/nfnetlink.h index 41d04e9d088a..0f47a4aa7fc4 100644 --- a/include/linux/netfilter/nfnetlink.h +++ b/include/linux/netfilter/nfnetlink.h @@ -66,7 +66,7 @@ static inline bool lockdep_nfnl_is_held(__u8 subsys_id) * @ss: The nfnetlink subsystem ID * * Return the value of the specified RCU-protected pointer, but omit - * both the smp_read_barrier_depends() and the ACCESS_ONCE(), because + * both the smp_read_barrier_depends() and the READ_ONCE(), because * caller holds the NFNL subsystem mutex. */ #define nfnl_dereference(p, ss) \ diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h index dea59c8eec54..765f7b915475 100644 --- a/include/linux/rtnetlink.h +++ b/include/linux/rtnetlink.h @@ -67,7 +67,7 @@ static inline bool lockdep_rtnl_is_held(void) * @p: The pointer to read, prior to dereferencing * * Return the value of the specified RCU-protected pointer, but omit - * both the smp_read_barrier_depends() and the ACCESS_ONCE(), because + * both the smp_read_barrier_depends() and the READ_ONCE(), because * caller holds RTNL. */ #define rtnl_dereference(p) \ diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h index 0f5b12a4ad09..5c68e279eaea 100644 --- a/include/net/netfilter/nf_tables.h +++ b/include/net/netfilter/nf_tables.h @@ -1164,8 +1164,8 @@ static inline u8 nft_genmask_next(const struct net *net) static inline u8 nft_genmask_cur(const struct net *net) { - /* Use ACCESS_ONCE() to prevent refetching the value for atomicity */ - return 1 << ACCESS_ONCE(net->nft.gencursor); + /* Use READ_ONCE() to prevent refetching the value for atomicity */ + return 1 << READ_ONCE(net->nft.gencursor); } #define NFT_GENMASK_ANY ((1 << 0) | (1 << 1)) diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c index 0e5b64a75da0..1cfffd42d1e2 100644 --- a/net/netfilter/ipvs/ip_vs_sync.c +++ b/net/netfilter/ipvs/ip_vs_sync.c @@ -457,7 +457,7 @@ static inline bool in_persistence(struct ip_vs_conn *cp) static int ip_vs_sync_conn_needed(struct netns_ipvs *ipvs, struct ip_vs_conn *cp, int pkts) { - unsigned long orig = ACCESS_ONCE(cp->sync_endtime); + unsigned long orig = READ_ONCE(cp->sync_endtime); unsigned long now = jiffies; unsigned long n = (now + cp->timeout) & ~3UL; unsigned int sync_refresh_period; diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c index c9796629858f..a16356cacec3 100644 --- a/net/netfilter/nfnetlink_queue.c +++ b/net/netfilter/nfnetlink_queue.c @@ -401,7 +401,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue, outdev = entry->state.out; - switch ((enum nfqnl_config_mode)ACCESS_ONCE(queue->copy_mode)) { + switch ((enum nfqnl_config_mode)READ_ONCE(queue->copy_mode)) { case NFQNL_COPY_META: case NFQNL_COPY_NONE: break; @@ -412,7 +412,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue, skb_checksum_help(entskb)) return NULL; - data_len = ACCESS_ONCE(queue->copy_range); + data_len = READ_ONCE(queue->copy_range); if (data_len > entskb->len) data_len = entskb->len; -- 2.5.2