doc: Spinlocks are implied RCU readers

[linux-2.6-microblaze.git] / Documentation / RCU / rcu_dereference.rst

diff --git a/Documentation/RCU/rcu_dereference.rst b/Documentation/RCU/rcu_dereference.rst
index 659d591..2524dcd 100644 (file)
--- a/Documentation/RCU/rcu_dereference.rst
+++ b/Documentation/RCU/rcu_dereference.rst
@@ -408,7 +408,10 @@ member of the rcu_dereference() to use in various situations:
        RCU flavors, an RCU read-side critical section is entered
        using rcu_read_lock(), anything that disables bottom halves,
        anything that disables interrupts, or anything that disables
-       preemption.
+       preemption.  Please note that spinlock critical sections
+       are also implied RCU read-side critical sections, even when
+       they are preemptible, as they are in kernels built with
+       CONFIG_PREEMPT_RT=y.
 
 2.     If the access might be within an RCU read-side critical section
        on the one hand, or protected by (say) my_lock on the other,