osq_lock() consults node->prev in the vcpu_is_preempted() heuristic while
a concurrent predecessor may update it via WRITE_ONCE(next->prev, prev)
during unqueue.
This read only affects the decision to abort optimistic spinning; stale
values do not affect queue linkage or lock correctness. Use READ_ONCE()
to mark the shared read and match the concurrent WRITE_ONCE() update.
No functional change intended.
Signed-off-by: Yu Peng <pengyu@kylinos.cn>
---
kernel/locking/osq_lock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c
index b4233dc2c2b04..db4545e7bb72c 100644
--- a/kernel/locking/osq_lock.c
+++ b/kernel/locking/osq_lock.c
@@ -144,7 +144,7 @@ bool osq_lock(struct optimistic_spin_queue *lock)
* polling, be careful.
*/
if (smp_cond_load_relaxed(&node->locked, VAL || need_resched() ||
- vcpu_is_preempted(node_cpu(node->prev))))
+ vcpu_is_preempted(node_cpu(READ_ONCE(node->prev)))))
return true;
/* unqueue */
--
2.43.0