[PATCH v2 tip/core/rcu 9/9] Convert ACCESS_ONCE() to READ_ONCE() and WRITE_ONCE() in update.c

Paul E. McKenney
2015-03-16T18:42:52Z

This commit moves kernel/rcu/update.c 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>
---
kernel/rcu/update.c | 30 +++++++++++++++---------------
1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 1f133350da01..afaecb7a799a 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -150,14 +150,14 @@ void __rcu_read_unlock(void)
barrier(); /* critical section before exit code. */
t->rcu_read_lock_nesting = INT_MIN;
barrier(); /* assign before ->rcu_read_unlock_special load */
- if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special.s)))
+ if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s)))
rcu_read_unlock_special(t);
barrier(); /* ->rcu_read_unlock_special load before assign */
t->rcu_read_lock_nesting = 0;
}
#ifdef CONFIG_PROVE_LOCKING
{
- int rrln = ACCESS_ONCE(t->rcu_read_lock_nesting);
+ int rrln = READ_ONCE(t->rcu_read_lock_nesting);

WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2);
}
@@ -389,17 +389,17 @@ module_param(rcu_cpu_stall_timeout, int, 0644);

int rcu_jiffies_till_stall_check(void)
{
- int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout);
+ int till_stall_check = READ_ONCE(rcu_cpu_stall_timeout);

/*
* Limit check must be consistent with the Kconfig limits
* for CONFIG_RCU_CPU_STALL_TIMEOUT.
*/
if (till_stall_check < 3) {
- ACCESS_ONCE(rcu_cpu_stall_timeout) = 3;
+ WRITE_ONCE(rcu_cpu_stall_timeout, 3);
till_stall_check = 3;
} else if (till_stall_check > 300) {
- ACCESS_ONCE(rcu_cpu_stall_timeout) = 300;
+ WRITE_ONCE(rcu_cpu_stall_timeout, 300);
till_stall_check = 300;
}
return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
@@ -550,12 +550,12 @@ static void check_holdout_task(struct task_struct *t,
{
int cpu;

- if (!ACCESS_ONCE(t->rcu_tasks_holdout) ||
- t->rcu_tasks_nvcsw != ACCESS_ONCE(t->nvcsw) ||
- !ACCESS_ONCE(t->on_rq) ||
+ if (!READ_ONCE(t->rcu_tasks_holdout) ||
+ t->rcu_tasks_nvcsw != READ_ONCE(t->nvcsw) ||
+ !READ_ONCE(t->on_rq) ||
(IS_ENABLED(CONFIG_NO_HZ_FULL) &&
!is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) {
- ACCESS_ONCE(t->rcu_tasks_holdout) = false;
+ WRITE_ONCE(t->rcu_tasks_holdout, false);
list_del_init(&t->rcu_tasks_holdout_list);
put_task_struct(t);
return;
@@ -639,11 +639,11 @@ static int __noreturn rcu_tasks_kthread(void *arg)
*/
rcu_read_lock();
for_each_process_thread(g, t) {
- if (t != current && ACCESS_ONCE(t->on_rq) &&
+ if (t != current && READ_ONCE(t->on_rq) &&
!is_idle_task(t)) {
get_task_struct(t);
- t->rcu_tasks_nvcsw = ACCESS_ONCE(t->nvcsw);
- ACCESS_ONCE(t->rcu_tasks_holdout) = true;
+ t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw);
+ WRITE_ONCE(t->rcu_tasks_holdout, true);
list_add(&t->rcu_tasks_holdout_list,
&rcu_tasks_holdouts);
}
@@ -672,7 +672,7 @@ static int __noreturn rcu_tasks_kthread(void *arg)
struct task_struct *t1;

schedule_timeout_interruptible(HZ);
- rtst = ACCESS_ONCE(rcu_task_stall_timeout);
+ rtst = READ_ONCE(rcu_task_stall_timeout);
needreport = rtst > 0 &&
time_after(jiffies, lastreport + rtst);
if (needreport)
@@ -728,7 +728,7 @@ static void rcu_spawn_tasks_kthread(void)
static struct task_struct *rcu_tasks_kthread_ptr;
struct task_struct *t;

- if (ACCESS_ONCE(rcu_tasks_kthread_ptr)) {
+ if (READ_ONCE(rcu_tasks_kthread_ptr)) {
smp_mb(); /* Ensure caller sees full kthread. */
return;
}
@@ -740,7 +740,7 @@ static void rcu_spawn_tasks_kthread(void)
t = kthread_run(rcu_tasks_kthread, NULL, "rcu_tasks_kthread");
BUG_ON(IS_ERR(t));
smp_mb(); /* Ensure others see full kthread. */
- ACCESS_ONCE(rcu_tasks_kthread_ptr) = t;
+ WRITE_ONCE(rcu_tasks_kthread_ptr, t);
mutex_unlock(&rcu_tasks_kthread_mutex);
}

--
1.8.1.5