rcu: Convert ACCESS_ONCE() to READ_ONCE() and WRITE_ONCE()
This commit moves from the old ACCESS_ONCE() API to the new READ_ONCE()
and WRITE_ONCE() APIs.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Updated to include kernel/torture.c as suggested by Jason Low. ]
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 8c0ec0f..58b1ebd 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -570,7 +570,7 @@
static int sync_rcu_preempt_exp_done(struct rcu_node *rnp)
{
return !rcu_preempted_readers_exp(rnp) &&
- ACCESS_ONCE(rnp->expmask) == 0;
+ READ_ONCE(rnp->expmask) == 0;
}
/*
@@ -716,7 +716,7 @@
int trycount = 0;
smp_mb(); /* Caller's modifications seen first by other CPUs. */
- snap = ACCESS_ONCE(sync_rcu_preempt_exp_count) + 1;
+ snap = READ_ONCE(sync_rcu_preempt_exp_count) + 1;
smp_mb(); /* Above access cannot bleed into critical section. */
/*
@@ -740,7 +740,7 @@
*/
while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) {
if (ULONG_CMP_LT(snap,
- ACCESS_ONCE(sync_rcu_preempt_exp_count))) {
+ READ_ONCE(sync_rcu_preempt_exp_count))) {
put_online_cpus();
goto mb_ret; /* Others did our work for us. */
}
@@ -752,7 +752,7 @@
return;
}
}
- if (ULONG_CMP_LT(snap, ACCESS_ONCE(sync_rcu_preempt_exp_count))) {
+ if (ULONG_CMP_LT(snap, READ_ONCE(sync_rcu_preempt_exp_count))) {
put_online_cpus();
goto unlock_mb_ret; /* Others did our work for us. */
}
@@ -780,8 +780,7 @@
/* Clean up and exit. */
smp_mb(); /* ensure expedited GP seen before counter increment. */
- ACCESS_ONCE(sync_rcu_preempt_exp_count) =
- sync_rcu_preempt_exp_count + 1;
+ WRITE_ONCE(sync_rcu_preempt_exp_count, sync_rcu_preempt_exp_count + 1);
unlock_mb_ret:
mutex_unlock(&sync_rcu_preempt_exp_mutex);
mb_ret:
@@ -994,8 +993,8 @@
struct task_struct *t;
struct list_head *tb;
- if (ACCESS_ONCE(rnp->exp_tasks) == NULL &&
- ACCESS_ONCE(rnp->boost_tasks) == NULL)
+ if (READ_ONCE(rnp->exp_tasks) == NULL &&
+ READ_ONCE(rnp->boost_tasks) == NULL)
return 0; /* Nothing left to boost. */
raw_spin_lock_irqsave(&rnp->lock, flags);
@@ -1048,8 +1047,8 @@
rt_mutex_lock(&rnp->boost_mtx);
rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */
- return ACCESS_ONCE(rnp->exp_tasks) != NULL ||
- ACCESS_ONCE(rnp->boost_tasks) != NULL;
+ return READ_ONCE(rnp->exp_tasks) != NULL ||
+ READ_ONCE(rnp->boost_tasks) != NULL;
}
/*
@@ -1462,7 +1461,7 @@
* callbacks not yet ready to invoke.
*/
if ((rdp->completed != rnp->completed ||
- unlikely(ACCESS_ONCE(rdp->gpwrap))) &&
+ unlikely(READ_ONCE(rdp->gpwrap))) &&
rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_NEXT_TAIL])
note_gp_changes(rsp, rdp);
@@ -1534,7 +1533,7 @@
int tne;
/* Handle nohz enablement switches conservatively. */
- tne = ACCESS_ONCE(tick_nohz_active);
+ tne = READ_ONCE(tick_nohz_active);
if (tne != rdtp->tick_nohz_enabled_snap) {
if (rcu_cpu_has_callbacks(NULL))
invoke_rcu_core(); /* force nohz to see update. */
@@ -1760,7 +1759,7 @@
atomic_read(&rdtp->dynticks) & 0xfff,
rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting,
rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
- ACCESS_ONCE(rsp->n_force_qs) - rsp->n_force_qs_gpstart,
+ READ_ONCE(rsp->n_force_qs) - rsp->n_force_qs_gpstart,
fast_no_hz);
}
@@ -1898,11 +1897,11 @@
{
struct rcu_data *rdp_leader = rdp->nocb_leader;
- if (!ACCESS_ONCE(rdp_leader->nocb_kthread))
+ if (!READ_ONCE(rdp_leader->nocb_kthread))
return;
- if (ACCESS_ONCE(rdp_leader->nocb_leader_sleep) || force) {
+ if (READ_ONCE(rdp_leader->nocb_leader_sleep) || force) {
/* Prior smp_mb__after_atomic() orders against prior enqueue. */
- ACCESS_ONCE(rdp_leader->nocb_leader_sleep) = false;
+ WRITE_ONCE(rdp_leader->nocb_leader_sleep, false);
wake_up(&rdp_leader->nocb_wq);
}
}
@@ -1934,14 +1933,14 @@
ret = atomic_long_read(&rdp->nocb_q_count);
#ifdef CONFIG_PROVE_RCU
- rhp = ACCESS_ONCE(rdp->nocb_head);
+ rhp = READ_ONCE(rdp->nocb_head);
if (!rhp)
- rhp = ACCESS_ONCE(rdp->nocb_gp_head);
+ rhp = READ_ONCE(rdp->nocb_gp_head);
if (!rhp)
- rhp = ACCESS_ONCE(rdp->nocb_follower_head);
+ rhp = READ_ONCE(rdp->nocb_follower_head);
/* Having no rcuo kthread but CBs after scheduler starts is bad! */
- if (!ACCESS_ONCE(rdp->nocb_kthread) && rhp &&
+ if (!READ_ONCE(rdp->nocb_kthread) && rhp &&
rcu_scheduler_fully_active) {
/* RCU callback enqueued before CPU first came online??? */
pr_err("RCU: Never-onlined no-CBs CPU %d has CB %p\n",
@@ -1975,12 +1974,12 @@
atomic_long_add(rhcount, &rdp->nocb_q_count);
/* rcu_barrier() relies on ->nocb_q_count add before xchg. */
old_rhpp = xchg(&rdp->nocb_tail, rhtp);
- ACCESS_ONCE(*old_rhpp) = rhp;
+ WRITE_ONCE(*old_rhpp, rhp);
atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy);
smp_mb__after_atomic(); /* Store *old_rhpp before _wake test. */
/* If we are not being polled and there is a kthread, awaken it ... */
- t = ACCESS_ONCE(rdp->nocb_kthread);
+ t = READ_ONCE(rdp->nocb_kthread);
if (rcu_nocb_poll || !t) {
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
TPS("WakeNotPoll"));
@@ -2118,7 +2117,7 @@
for (;;) {
wait_event_interruptible(
rnp->nocb_gp_wq[c & 0x1],
- (d = ULONG_CMP_GE(ACCESS_ONCE(rnp->completed), c)));
+ (d = ULONG_CMP_GE(READ_ONCE(rnp->completed), c)));
if (likely(d))
break;
WARN_ON(signal_pending(current));
@@ -2145,7 +2144,7 @@
if (!rcu_nocb_poll) {
trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Sleep");
wait_event_interruptible(my_rdp->nocb_wq,
- !ACCESS_ONCE(my_rdp->nocb_leader_sleep));
+ !READ_ONCE(my_rdp->nocb_leader_sleep));
/* Memory barrier handled by smp_mb() calls below and repoll. */
} else if (firsttime) {
firsttime = false; /* Don't drown trace log with "Poll"! */
@@ -2159,12 +2158,12 @@
*/
gotcbs = false;
for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) {
- rdp->nocb_gp_head = ACCESS_ONCE(rdp->nocb_head);
+ rdp->nocb_gp_head = READ_ONCE(rdp->nocb_head);
if (!rdp->nocb_gp_head)
continue; /* No CBs here, try next follower. */
/* Move callbacks to wait-for-GP list, which is empty. */
- ACCESS_ONCE(rdp->nocb_head) = NULL;
+ WRITE_ONCE(rdp->nocb_head, NULL);
rdp->nocb_gp_tail = xchg(&rdp->nocb_tail, &rdp->nocb_head);
gotcbs = true;
}
@@ -2184,7 +2183,7 @@
my_rdp->nocb_leader_sleep = true;
smp_mb(); /* Ensure _sleep true before scan. */
for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower)
- if (ACCESS_ONCE(rdp->nocb_head)) {
+ if (READ_ONCE(rdp->nocb_head)) {
/* Found CB, so short-circuit next wait. */
my_rdp->nocb_leader_sleep = false;
break;
@@ -2205,7 +2204,7 @@
/* Each pass through the following loop wakes a follower, if needed. */
for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) {
- if (ACCESS_ONCE(rdp->nocb_head))
+ if (READ_ONCE(rdp->nocb_head))
my_rdp->nocb_leader_sleep = false;/* No need to sleep.*/
if (!rdp->nocb_gp_head)
continue; /* No CBs, so no need to wake follower. */
@@ -2241,7 +2240,7 @@
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
"FollowerSleep");
wait_event_interruptible(rdp->nocb_wq,
- ACCESS_ONCE(rdp->nocb_follower_head));
+ READ_ONCE(rdp->nocb_follower_head));
} else if (firsttime) {
/* Don't drown trace log with "Poll"! */
firsttime = false;
@@ -2282,10 +2281,10 @@
nocb_follower_wait(rdp);
/* Pull the ready-to-invoke callbacks onto local list. */
- list = ACCESS_ONCE(rdp->nocb_follower_head);
+ list = READ_ONCE(rdp->nocb_follower_head);
BUG_ON(!list);
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "WokeNonEmpty");
- ACCESS_ONCE(rdp->nocb_follower_head) = NULL;
+ WRITE_ONCE(rdp->nocb_follower_head, NULL);
tail = xchg(&rdp->nocb_follower_tail, &rdp->nocb_follower_head);
/* Each pass through the following loop invokes a callback. */
@@ -2324,7 +2323,7 @@
/* Is a deferred wakeup of rcu_nocb_kthread() required? */
static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp)
{
- return ACCESS_ONCE(rdp->nocb_defer_wakeup);
+ return READ_ONCE(rdp->nocb_defer_wakeup);
}
/* Do a deferred wakeup of rcu_nocb_kthread(). */
@@ -2334,8 +2333,8 @@
if (!rcu_nocb_need_deferred_wakeup(rdp))
return;
- ndw = ACCESS_ONCE(rdp->nocb_defer_wakeup);
- ACCESS_ONCE(rdp->nocb_defer_wakeup) = RCU_NOGP_WAKE_NOT;
+ ndw = READ_ONCE(rdp->nocb_defer_wakeup);
+ WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOGP_WAKE_NOT);
wake_nocb_leader(rdp, ndw == RCU_NOGP_WAKE_FORCE);
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("DeferredWake"));
}
@@ -2448,7 +2447,7 @@
t = kthread_run(rcu_nocb_kthread, rdp_spawn,
"rcuo%c/%d", rsp->abbr, cpu);
BUG_ON(IS_ERR(t));
- ACCESS_ONCE(rdp_spawn->nocb_kthread) = t;
+ WRITE_ONCE(rdp_spawn->nocb_kthread, t);
}
/*
@@ -2663,7 +2662,7 @@
/* Record start of fully idle period. */
j = jiffies;
- ACCESS_ONCE(rdtp->dynticks_idle_jiffies) = j;
+ WRITE_ONCE(rdtp->dynticks_idle_jiffies, j);
smp_mb__before_atomic();
atomic_inc(&rdtp->dynticks_idle);
smp_mb__after_atomic();
@@ -2681,7 +2680,7 @@
*/
void rcu_sysidle_force_exit(void)
{
- int oldstate = ACCESS_ONCE(full_sysidle_state);
+ int oldstate = READ_ONCE(full_sysidle_state);
int newoldstate;
/*
@@ -2794,7 +2793,7 @@
smp_mb(); /* Read counters before timestamps. */
/* Pick up timestamps. */
- j = ACCESS_ONCE(rdtp->dynticks_idle_jiffies);
+ j = READ_ONCE(rdtp->dynticks_idle_jiffies);
/* If this CPU entered idle more recently, update maxj timestamp. */
if (ULONG_CMP_LT(*maxj, j))
*maxj = j;
@@ -2831,11 +2830,11 @@
static void rcu_sysidle(unsigned long j)
{
/* Check the current state. */
- switch (ACCESS_ONCE(full_sysidle_state)) {
+ switch (READ_ONCE(full_sysidle_state)) {
case RCU_SYSIDLE_NOT:
/* First time all are idle, so note a short idle period. */
- ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_SHORT;
+ WRITE_ONCE(full_sysidle_state, RCU_SYSIDLE_SHORT);
break;
case RCU_SYSIDLE_SHORT:
@@ -2873,7 +2872,7 @@
{
smp_mb();
if (full_sysidle_state > RCU_SYSIDLE_SHORT)
- ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_NOT;
+ WRITE_ONCE(full_sysidle_state, RCU_SYSIDLE_NOT);
}
/*
@@ -2925,7 +2924,7 @@
smp_mb(); /* grace period precedes setting inuse. */
rshp = container_of(rhp, struct rcu_sysidle_head, rh);
- ACCESS_ONCE(rshp->inuse) = 0;
+ WRITE_ONCE(rshp->inuse, 0);
}
/*
@@ -2936,7 +2935,7 @@
bool rcu_sys_is_idle(void)
{
static struct rcu_sysidle_head rsh;
- int rss = ACCESS_ONCE(full_sysidle_state);
+ int rss = READ_ONCE(full_sysidle_state);
if (WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu))
return false;
@@ -2964,7 +2963,7 @@
}
rcu_sysidle_report(rcu_state_p, isidle, maxj, false);
oldrss = rss;
- rss = ACCESS_ONCE(full_sysidle_state);
+ rss = READ_ONCE(full_sysidle_state);
}
}
@@ -3048,7 +3047,7 @@
#ifdef CONFIG_NO_HZ_FULL
if (tick_nohz_full_cpu(smp_processor_id()) &&
(!rcu_gp_in_progress(rsp) ||
- ULONG_CMP_LT(jiffies, ACCESS_ONCE(rsp->gp_start) + HZ)))
+ ULONG_CMP_LT(jiffies, READ_ONCE(rsp->gp_start) + HZ)))
return 1;
#endif /* #ifdef CONFIG_NO_HZ_FULL */
return 0;
@@ -3077,7 +3076,7 @@
static void rcu_dynticks_task_enter(void)
{
#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
- ACCESS_ONCE(current->rcu_tasks_idle_cpu) = smp_processor_id();
+ WRITE_ONCE(current->rcu_tasks_idle_cpu, smp_processor_id());
#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
}
@@ -3085,6 +3084,6 @@
static void rcu_dynticks_task_exit(void)
{
#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
- ACCESS_ONCE(current->rcu_tasks_idle_cpu) = -1;
+ WRITE_ONCE(current->rcu_tasks_idle_cpu, -1);
#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
}