These changes are the raw update to linux-4.4.6-rt14. Kernel sources

[kvmfornfv.git] / kernel / kernel / locking / osq_lock.c

diff --git a/kernel/kernel/locking/osq_lock.c b/kernel/kernel/locking/osq_lock.c
index dc85ee2..05a3785 100644 (file)
--- a/kernel/kernel/locking/osq_lock.c
+++ b/kernel/kernel/locking/osq_lock.c
@@ -50,7 +50,7 @@ osq_wait_next(struct optimistic_spin_queue *lock,
 
        for (;;) {
                if (atomic_read(&lock->tail) == curr &&
-                   atomic_cmpxchg(&lock->tail, curr, old) == curr) {
+                   atomic_cmpxchg_acquire(&lock->tail, curr, old) == curr) {
                        /*
                         * We were the last queued, we moved @lock back. @prev
                         * will now observe @lock and will complete its
@@ -92,6 +92,12 @@ bool osq_lock(struct optimistic_spin_queue *lock)
        node->next = NULL;
        node->cpu = curr;
 
+       /*
+        * We need both ACQUIRE (pairs with corresponding RELEASE in
+        * unlock() uncontended, or fastpath) and RELEASE (to publish
+        * the node fields we just initialised) semantics when updating
+        * the lock tail.
+        */
        old = atomic_xchg(&lock->tail, curr);
        if (old == OSQ_UNLOCKED_VAL)
                return true;
@@ -184,7 +190,8 @@ void osq_unlock(struct optimistic_spin_queue *lock)
        /*
         * Fast path for the uncontended case.
         */
-       if (likely(atomic_cmpxchg(&lock->tail, curr, OSQ_UNLOCKED_VAL) == curr))
+       if (likely(atomic_cmpxchg_release(&lock->tail, curr,
+                                         OSQ_UNLOCKED_VAL) == curr))
                return;
 
        /*