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-rw-r--r--kernel/rcu/tree_exp.h16
1 files changed, 15 insertions, 1 deletions
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 8a1d9c8bd9f7..1dbad2442e8d 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -357,7 +357,21 @@ static void __sync_rcu_exp_select_node_cpus(struct rcu_exp_work *rewp)
!(rnp->qsmaskinitnext & mask)) {
mask_ofl_test |= mask;
} else {
- snap = rcu_dynticks_snap(cpu);
+ /*
+ * Full ordering between remote CPU's post idle accesses
+ * and updater's accesses prior to current GP (and also
+ * the started GP sequence number) is enforced by
+ * rcu_seq_start() implicit barrier, relayed by kworkers
+ * locking and even further by smp_mb__after_unlock_lock()
+ * barriers chained all the way throughout the rnp locking
+ * tree since sync_exp_reset_tree() and up to the current
+ * leaf rnp locking.
+ *
+ * Ordering between remote CPU's pre idle accesses and
+ * post grace period updater's accesses is enforced by the
+ * below acquire semantic.
+ */
+ snap = ct_dynticks_cpu_acquire(cpu);
if (rcu_dynticks_in_eqs(snap))
mask_ofl_test |= mask;
else