doc: rcu: Add more rationale for using rcu_read_lock_sched in checklist

This commit explains why rcu_read_lock_sched is better than using
preempt_disable.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt
index 49747717d90579d02abd6c07f5b34cf9f3543ee6..8860ab2a897ae237062d2dc80b85a4e5b1a4d928 100644 (file)
--- a/Documentation/RCU/checklist.txt
+++ b/Documentation/RCU/checklist.txt
@@ -63,7 +63,7 @@ over a rather long period of time, but improvements are always welcome!
        pointer must be covered by rcu_read_lock(), rcu_read_lock_bh(),
        rcu_read_lock_sched(), or by the appropriate update-side lock.
        Disabling of preemption can serve as rcu_read_lock_sched(), but
-       is less readable.
+       is less readable and prevents lockdep from detecting locking issues.
 
        Letting RCU-protected pointers "leak" out of an RCU read-side
        critical section is every bid as bad as letting them leak out