From 14cd5d4a0125f643350e7fa12f5384f1fc2d3e9d Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Mon, 23 Oct 2017 14:07:17 -0700 Subject: [PATCH] locking/atomics, net/netlink/netfilter: Convert ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE() 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 Signed-off-by: Paul E. McKenney Cc: David S. Miller Cc: Florian Westphal Cc: Jozsef Kadlecsik Cc: Linus Torvalds Cc: Pablo Neira Ayuso Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-arch@vger.kernel.org Cc: mpe@ellerman.id.au Cc: shuah@kernel.org Cc: snitzer@redhat.com Cc: thor.thayer@linux.intel.com Cc: tj@kernel.org Cc: viro@zeniv.linux.org.uk Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1508792849-3115-7-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar --- 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 a4c61cb..0e694cf 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 41d04e9..0f47a4a 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 dea59c8..765f7b9 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 0f5b12a4..5c68e27 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 0e5b64a..1cfffd4 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 c979662..a16356c 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; -- 2.7.4