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 <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Florian Westphal <fw@strlen.de>
Cc: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
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 <mingo@kernel.org>
* @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) \
* @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) \
* @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) \
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))
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;
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;
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;