-//$$CDS-header$$
+/*
+ This file is a part of libcds - Concurrent Data Structures library
+
+ (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2017
+
+ Source code repo: http://github.com/khizmax/libcds/
+ Download: http://sourceforge.net/projects/libcds/files/
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions are met:
+
+ * Redistributions of source code must retain the above copyright notice, this
+ list of conditions and the following disclaimer.
+
+ * Redistributions in binary form must reproduce the above copyright notice,
+ this list of conditions and the following disclaimer in the documentation
+ and/or other materials provided with the distribution.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
#ifndef CDSLIB_SYNC_MONITOR_H
#define CDSLIB_SYNC_MONITOR_H
#include <cds/details/defs.h>
namespace cds { namespace sync {
-
/**
@page cds_sync_monitor Synchronization monitor
-
- A <a href="http://en.wikipedia.org/wiki/Monitor_%28synchronization%29">monitor</a> is synchronization construct
+ A <a href="http://en.wikipedia.org/wiki/Monitor_%28synchronization%29">monitor</a> is synchronization construction
that allows threads to have both mutual exclusion and the ability to wait (block) for a certain condition to become true.
-
Some blocking data structure algoritms like the trees require per-node locking.
For huge trees containing millions of nodes it can be very inefficient to inject
the lock object into each node. Moreover, some operating systems may not support
the millions of system objects like mutexes per user process.
-
The monitor strategy is intended to solve that problem.
When the node should be locked, the monitor is called to allocate appropriate
- lock object for the node if it's needed, and to lock the node.
+ lock object for the node if needed, and to lock the node.
The monitor strategy can significantly reduce the number of system objects
- required for the data structure.
+ required for data structure.
- <b>Implemetatios</b>
+ <b>Implemetations</b>
\p libcds contains several monitor implementations:
- \p sync::injecting_monitor injects the lock object into each node.
That mock monitor is designed for user-space locking primitive like
\ref sync::spin_lock "spin-lock".
+ - \p sync::pool_monitor is the monitor that allocates a lock object
+ for a node from the pool when needed. When the node is unlocked
+ the lock assigned to it is given back to the pool if no thread
+ references to that node.
<b>How to use</b>
If you use a container from \p libcds that requires a monitor, you should just
- specify required monitor type in container's traits. Usually, the monitor
+ specify required monitor type in container's traits. Usually, the monitor
is specified by \p traits::sync_monitor typedef, or by \p cds::opt::sync_monitor
option for container's \p make_traits metafunction.
- If you're developing a new container algorithm, you should know internal monitor
+ If you're developing a new container algorithm, you should know internal monitor
interface:
\code
class Monitor {
public:
// Monitor's injection into the Node class
template <typename Node>
- struct node_wrapper;
-
- // Locks the node
+ struct node_injection: public Node
+ {
+ // Monitor data injecting into container's node
+ // ...
+ };
+ // Locks the node
template <typename Node>
void lock( Node& node );
-
// Unlocks the node
template <typename Node>
void unlock( Node& node );
-
// Scoped lock applyes RAII to Monitor
template <typename Node>
- class scoped_lock
- {
- public:
- // Locks node by monitor mon
- scoped_lock( Monitor& mon, Node& node );
-
- // Unlocks the node locked by ctor
- ~scoped_lock();
- };
+ using scoped_lock = monitor_scoped_lock< pool_monitor, Node >;
};
\endcode
- The monitor should be a member of your container:
+ Monitor's data must be injected into container's node as \p m_SyncMonitorInjection data member:
+ \code
+ template <typename SyncMonitor>
+ struct my_node
+ {
+ // ...
+ typename SyncMonitor::node_injection m_SyncMonitorInjection;
+ };
+ \endcode
+ The monitor must be a member of your container:
\code
template <typename GC, typename T, typename Traits>
class my_container {
// ...
typedef typename Traits::sync_monitor sync_monitor;
+ typedef my_node<sync_monitor> node_type;
sync_monitor m_Monitor;
//...
};
\endcode
*/
-
+ /// Monitor scoped lock (RAII)
+ /**
+ Template arguments:
+ - \p Monitor - monitor type
+ - \p Node - node type
+ */
+ template <typename Monitor, typename Node>
+ struct monitor_scoped_lock
+ {
+ public:
+ typedef Monitor monitor_type; ///< Monitor type
+ typedef Node node_type; ///< Node type
+ private:
+ //@cond
+ monitor_type& m_Monitor; ///< Monitor
+ node_type const& m_Node; ///< Our locked node
+ //@endcond
+ public:
+ /// Makes exclusive access to the node \p p by \p monitor
+ monitor_scoped_lock( monitor_type& monitor, node_type const& p )
+ : m_Monitor( monitor )
+ , m_Node( p )
+ {
+ monitor.lock( p );
+ }
+ /// Unlocks the node
+ ~monitor_scoped_lock()
+ {
+ m_Monitor.unlock( m_Node );
+ }
+ };
}} // namespace cds::sync
-
#endif // #ifndef CDSLIB_SYNC_MONITOR_H
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