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-rw-r--r--Documentation/RCU/lockdep.txt34
1 files changed, 25 insertions, 9 deletions
diff --git a/Documentation/RCU/lockdep.txt b/Documentation/RCU/lockdep.txt
index d7a49b2f6994..a102d4b3724b 100644
--- a/Documentation/RCU/lockdep.txt
+++ b/Documentation/RCU/lockdep.txt
@@ -32,9 +32,27 @@ checking of rcu_dereference() primitives:
srcu_dereference(p, sp):
Check for SRCU read-side critical section.
rcu_dereference_check(p, c):
- Use explicit check expression "c". This is useful in
- code that is invoked by both readers and updaters.
- rcu_dereference_raw(p)
+ Use explicit check expression "c" along with
+ rcu_read_lock_held(). This is useful in code that is
+ invoked by both RCU readers and updaters.
+ rcu_dereference_bh_check(p, c):
+ Use explicit check expression "c" along with
+ rcu_read_lock_bh_held(). This is useful in code that
+ is invoked by both RCU-bh readers and updaters.
+ rcu_dereference_sched_check(p, c):
+ Use explicit check expression "c" along with
+ rcu_read_lock_sched_held(). This is useful in code that
+ is invoked by both RCU-sched readers and updaters.
+ srcu_dereference_check(p, c):
+ Use explicit check expression "c" along with
+ srcu_read_lock_held()(). This is useful in code that
+ is invoked by both SRCU readers and updaters.
+ rcu_dereference_index_check(p, c):
+ Use explicit check expression "c", but the caller
+ must supply one of the rcu_read_lock_held() functions.
+ This is useful in code that uses RCU-protected arrays
+ that is invoked by both RCU readers and updaters.
+ rcu_dereference_raw(p):
Don't check. (Use sparingly, if at all.)
rcu_dereference_protected(p, c):
Use explicit check expression "c", and omit all barriers
@@ -48,13 +66,11 @@ 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 +78,7 @@ 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.