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, 4 insertions, 4 deletions

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 43bf25ef3c81..16b2d3cc88b0 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -266,7 +266,7 @@ static inline int mutex_can_spin_on_owner(struct mutex *lock)
                 return 0;
 
         rcu_read_lock();
-        owner = ACCESS_ONCE(lock->owner);
+        owner = READ_ONCE(lock->owner);
         if (owner)
                 retval = owner->on_cpu;
         rcu_read_unlock();
@@ -340,7 +340,7 @@ static bool mutex_optimistic_spin(struct mutex *lock,
                          * As such, when deadlock detection needs to be
                          * performed the optimistic spinning cannot be done.
                          */
-                        if (ACCESS_ONCE(ww->ctx))
+                        if (READ_ONCE(ww->ctx))
                                 break;
                 }
 
@@ -348,7 +348,7 @@ static bool mutex_optimistic_spin(struct mutex *lock,
                  * If there's an owner, wait for it to either
                  * release the lock or go to sleep.
                  */
-                owner = ACCESS_ONCE(lock->owner);
+                owner = READ_ONCE(lock->owner);
                 if (owner && !mutex_spin_on_owner(lock, owner))
                         break;
 
@@ -487,7 +487,7 @@ static inline int __sched
 __ww_mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)
 {
         struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
-        struct ww_acquire_ctx *hold_ctx = ACCESS_ONCE(ww->ctx);
+        struct ww_acquire_ctx *hold_ctx = READ_ONCE(ww->ctx);
 
         if (!hold_ctx)
                 return 0;