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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-01-20 14:01:31 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-01-20 14:01:31 -0300
commitb4b7ff4b08e691656c9d77c758fc355833128ac0 (patch)
tree82fcb00e6b918026dc9f2d1f05ed8eee83874cc0 /kernel/locking/osq_lock.c
parent35acfa0fc609f2a2cd95cef4a6a9c3a5c38f1778 (diff)
Linux-libre 4.4-gnupck-4.4-gnu
Diffstat (limited to 'kernel/locking/osq_lock.c')
-rw-r--r--kernel/locking/osq_lock.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c
index dc85ee23a..05a37857a 100644
--- a/kernel/locking/osq_lock.c
+++ b/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;
/*