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-rw-r--r--kernel/locking/qspinlock.c13
1 files changed, 7 insertions, 6 deletions
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 38ece035039e..348c8cec1042 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -408,14 +408,15 @@ queue:
*/
if (old & _Q_TAIL_MASK) {
prev = decode_tail(old);
+
/*
- * The above xchg_tail() is also a load of @lock which
- * generates, through decode_tail(), a pointer. The address
- * dependency matches the RELEASE of xchg_tail() such that
- * the subsequent access to @prev happens after.
+ * We must ensure that the stores to @node are observed before
+ * the write to prev->next. The address dependency from
+ * xchg_tail is not sufficient to ensure this because the read
+ * component of xchg_tail is unordered with respect to the
+ * initialisation of @node.
*/
-
- WRITE_ONCE(prev->next, node);
+ smp_store_release(&prev->next, node);
pv_wait_node(node, prev);
arch_mcs_spin_lock_contended(&node->locked);