locking: Remove ACCESS_ONCE() usage

With the new standardized functions, we can replace all
ACCESS_ONCE() calls across relevant locking - this includes
lockref and seqlock while at it.

ACCESS_ONCE() does not work reliably on non-scalar types.
For example gcc 4.6 and 4.7 might remove the volatile tag
for such accesses during the SRA (scalar replacement of
aggregates) step:

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145

Update the new calls regardless of if it is a scalar type,
this is cleaner than having three alternatives.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1424662301.6539.18.camel@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index e4ad019e23f5..06e2214edf98 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -279,7 +279,7 @@ static inline bool rwsem_try_write_lock(long count, struct rw_semaphore *sem)
  */
 static inline bool rwsem_try_write_lock_unqueued(struct rw_semaphore *sem)
 {
-        long old, count = ACCESS_ONCE(sem->count);
+        long old, count = READ_ONCE(sem->count);
 
         while (true) {
                 if (!(count == 0 || count == RWSEM_WAITING_BIAS))
@@ -304,9 +304,9 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
                 return false;
 
         rcu_read_lock();
-        owner = ACCESS_ONCE(sem->owner);
+        owner = READ_ONCE(sem->owner);
         if (!owner) {
-                long count = ACCESS_ONCE(sem->count);
+                long count = READ_ONCE(sem->count);
                 /*
                  * If sem->owner is not set, yet we have just recently entered the
                  * slowpath with the lock being active, then there is a possibility
@@ -385,7 +385,7 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem)
                 goto done;
 
         while (true) {
-                owner = ACCESS_ONCE(sem->owner);
+                owner = READ_ONCE(sem->owner);
                 if (owner && !rwsem_spin_on_owner(sem, owner))
                         break;
 
@@ -459,7 +459,7 @@ struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem)
 
         /* we're now waiting on the lock, but no longer actively locking */
         if (waiting) {
-                count = ACCESS_ONCE(sem->count);
+                count = READ_ONCE(sem->count);
 
                 /*
                  * If there were already threads queued before us and there are