urcu: add rcu_list_iteration_adapter

Like its list_iteration_adapter counterpart, this utility allows
the iteration over cds_list structures and provides ranged-for
semantics.

This utility differs in that it provides an RCU-protected iteration
over the list.

Change-Id: I810126ee5e099a6e6bb15509d00efa0ebfa56e73
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/common/urcu.hpp b/src/common/urcu.hpp
index b59c2282c261fc31ee1676a5482092bffcd83090..6466fac4309896c531a7e85c7226f09af28b62b0 100644 (file)
--- a/src/common/urcu.hpp
+++ b/src/common/urcu.hpp
@@ -366,6 +366,58 @@ protected:
        cds_list_head& _list;
 };
 
+template <typename ContainedType, cds_list_head ContainedType::*Member>
+class rcu_list_iteration_adapter : public list_iteration_adapter<ContainedType, Member> {
+public:
+       /* Nested iterator class defines the iterator for rcu_list_iteration_adapter. */
+       class iterator : public list_iteration_adapter<ContainedType, Member>::iterator {
+               /* Allow rcu_list_iteration_adapter to access private members of iterator. */
+               friend rcu_list_iteration_adapter;
+
+       public:
+               iterator(const iterator& other) = default;
+               iterator(iterator&& other) noexcept = default;
+               ~iterator() = default;
+               iterator& operator=(const iterator&) = delete;
+               iterator& operator=(iterator&&) noexcept = delete;
+
+               /* Move to the next element in the hash table. */
+               iterator& operator++()
+               {
+                       this->_node = rcu_dereference(this->_node_contents.next);
+                       this->_node_contents = *this->_node;
+                       return *this;
+               }
+
+       protected:
+               explicit iterator(const cds_list_head& node) :
+                       list_iteration_adapter<ContainedType, Member>::iterator(node)
+               {
+               }
+       };
+
+       explicit rcu_list_iteration_adapter(cds_list_head& list) :
+               list_iteration_adapter<ContainedType, Member>(list)
+       {
+       }
+
+       /* Return an iterator to the beginning of the hash table. */
+       iterator begin() const noexcept
+       {
+               return iterator(*rcu_dereference(this->_list.next));
+       }
+
+       /* Return an iterator to the end of the hash table. */
+       iterator end() const noexcept
+       {
+               return iterator(this->_list);
+       }
+
+protected:
+       /* RCU read lock held during the iteration. */
+       const lttng::urcu::read_lock_guard read_lock;
+};
+
 } /* namespace urcu */
 } /* namespace lttng */