rcu: Add documentation for raw SRCU read-side primitives

Update various files in Documentation/RCU to reflect srcu_read_lock_raw()
and srcu_read_unlock_raw().  Credit to Peter Zijlstra for suggesting
use of the existing _raw suffix instead of the earlier bulkref names.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt
index 0c134f8afc6f..bff2d8be1e18 100644
--- a/Documentation/RCU/checklist.txt
+++ b/Documentation/RCU/checklist.txt
@@ -328,6 +328,12 @@ over a rather long period of time, but improvements are always welcome!
         RCU rather than SRCU, because RCU is almost always faster and
         easier to use than is SRCU.
 
+        If you need to enter your read-side critical section in a
+        hardirq or exception handler, and then exit that same read-side
+        critical section in the task that was interrupted, then you need
+        to srcu_read_lock_raw() and srcu_read_unlock_raw(), which avoid
+        the lockdep checking that would otherwise this practice illegal.
+
         Also unlike other forms of RCU, explicit initialization
         and cleanup is required via init_srcu_struct() and
         cleanup_srcu_struct().  These are passed a "struct srcu_struct"