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-rw-r--r--kernel/rcu/tree.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index b2bccfd37c38..d540d210e5c7 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2145,6 +2145,12 @@ static void rcu_do_batch(struct rcu_data *rdp)
* Extract the list of ready callbacks, disabling IRQs to prevent
* races with call_rcu() from interrupt handlers. Leave the
* callback counts, as rcu_barrier() needs to be conservative.
+ *
+ * Callbacks execution is fully ordered against preceding grace period
+ * completion (materialized by rnp->gp_seq update) thanks to the
+ * smp_mb__after_unlock_lock() upon node locking required for callbacks
+ * advancing. In NOCB mode this ordering is then further relayed through
+ * the nocb locking that protects both callbacks advancing and extraction.
*/
rcu_nocb_lock_irqsave(rdp, flags);
WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));