3 #ifndef CDSLIB_SYNC_MONITOR_H
4 #define CDSLIB_SYNC_MONITOR_H
6 #include <cds/details/defs.h>
8 namespace cds { namespace sync {
11 @page cds_sync_monitor Synchronization monitor
13 A <a href="http://en.wikipedia.org/wiki/Monitor_%28synchronization%29">monitor</a> is synchronization construct
14 that allows threads to have both mutual exclusion and the ability to wait (block) for a certain condition to become true.
16 Some blocking data structure algoritms like the trees require per-node locking.
17 For huge trees containing millions of nodes it can be very inefficient to inject
18 the lock object into each node. Moreover, some operating systems may not support
19 the millions of system objects like mutexes per user process.
21 The monitor strategy is intended to solve that problem.
22 When the node should be locked, the monitor is called to allocate appropriate
23 lock object for the node if it's needed, and to lock the node.
24 The monitor strategy can significantly reduce the number of system objects
25 required for data structure.
29 \p libcds contains several monitor implementations:
30 - \p sync::injecting_monitor injects the lock object into each node.
31 That mock monitor is designed for user-space locking primitive like
32 \ref sync::spin_lock "spin-lock".
33 - \p sync::pool_monitor is the monitor that allocates the lock object
34 for the node from the pool when needed. When the node is unlocked
35 the lock assigned to it is given back to the pool if no thread
36 references to that node.
40 If you use a container from \p libcds that requires a monitor, you should just
41 specify required monitor type in container's traits. Usually, the monitor
42 is specified by \p traits::sync_monitor typedef, or by \p cds::opt::sync_monitor
43 option for container's \p make_traits metafunction.
45 If you're developing a new container algorithm, you should know internal monitor
50 // Monitor's injection into the Node class
51 template <typename Node>
52 struct node_injection: public Node
54 // Monitor data to inject into container's node
59 template <typename Node>
60 void lock( Node& node );
63 template <typename Node>
64 void unlock( Node& node );
66 // Scoped lock applyes RAII to Monitor
67 template <typename Node>
68 using scoped_lock = monitor_scoped_lock< pool_monitor, Node >;
71 The monitor should be a member of your container:
73 template <typename GC, typename T, typename Traits>
76 typedef typename Traits::sync_monitor sync_monitor;
77 sync_monitor m_Monitor;
83 /// Monitor scoped lock (RAII)
86 - \p Monitor - monitor type
89 template <typename Monitor, typename Node>
90 struct monitor_scoped_lock
93 typedef Monitor monitor_type; ///< Monitor type
94 typedef Node node_type; ///< Node type
98 monitor_type& m_Monitor; ///< Monitor
99 node_type const& m_Node; ///< Our locked node
103 /// Makes exclusive access to the node \p p by \p monitor
104 scoped_lock( monitor_type& monitor, node_type const& p )
105 : m_Monitor( monitor )
114 m_Monitor.unlock( m_Node );
118 }} // namespace cds::sync
120 #endif // #ifndef CDSLIB_SYNC_MONITOR_H