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Diffstat (limited to 'Documentation/RCU/lockdep.txt')
| -rw-r--r-- | Documentation/RCU/lockdep.txt | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/Documentation/RCU/lockdep.txt b/Documentation/RCU/lockdep.txt index da51d3068850..89db949eeca0 100644 --- a/Documentation/RCU/lockdep.txt +++ b/Documentation/RCU/lockdep.txt @@ -96,7 +96,17 @@ other flavors of rcu_dereference(). On the other hand, it is illegal to use rcu_dereference_protected() if either the RCU-protected pointer or the RCU-protected data that it points to can change concurrently. -There are currently only "universal" versions of the rcu_assign_pointer() -and RCU list-/tree-traversal primitives, which do not (yet) check for -being in an RCU read-side critical section. In the future, separate -versions of these primitives might be created. +Like rcu_dereference(), when lockdep is enabled, RCU list and hlist +traversal primitives check for being called from within an RCU read-side +critical section. However, a lockdep expression can be passed to them +as a additional optional argument. With this lockdep expression, these +traversal primitives will complain only if the lockdep expression is +false and they are called from outside any RCU read-side critical section. + +For example, the workqueue for_each_pwq() macro is intended to be used +either within an RCU read-side critical section or with wq->mutex held. +It is thus implemented as follows: + + #define for_each_pwq(pwq, wq) + list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node, + lock_is_held(&(wq->mutex).dep_map)) |