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Subject[PATCH tip/core/rcu 24/55] rcu: Not necessary to pass rcu_read_lock_held() to rcu_dereference_protected()
From: Michal Hocko <>

Since ca5ecddf (rcu: define __rcu address space modifier for sparse)
rcu_dereference_check() use rcu_read_lock_held() as a part of condition
automatically. Therefore, callers of rcu_dereference_check() no longer
need to pass rcu_read_lock_held() to rcu_dereference_check().

Signed-off-by: Michal Hocko <>
Signed-off-by: Paul E. McKenney <>
Documentation/RCU/lockdep.txt | 10 ++++------
1 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/Documentation/RCU/lockdep.txt b/Documentation/RCU/lockdep.txt
index d7a49b2..4998c63 100644
--- a/Documentation/RCU/lockdep.txt
+++ b/Documentation/RCU/lockdep.txt
@@ -48,13 +48,11 @@ checking of rcu_dereference() primitives:
value of the pointer itself, for example, against NULL.

The rcu_dereference_check() check expression can be any boolean
-expression, but would normally include one of the rcu_read_lock_held()
-family of functions and a lockdep expression. However, any boolean
-expression can be used. For a moderately ornate example, consider
-the following:
+expression, but would normally include a lockdep expression. However,
+any boolean expression can be used. For a moderately ornate example,
+consider the following:

file = rcu_dereference_check(fdt->fd[fd],
- rcu_read_lock_held() ||
lockdep_is_held(&files->file_lock) ||
atomic_read(&files->count) == 1);

@@ -62,7 +60,7 @@ This expression picks up the pointer "fdt->fd[fd]" in an RCU-safe manner,
and, if CONFIG_PROVE_RCU is configured, verifies that this expression
is used in:

-1. An RCU read-side critical section, or
+1. An RCU read-side critical section (implicit), or
2. with files->file_lock held, or
3. on an unshared files_struct.


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