3 #ifndef _CDS_URCU_DETAILS_GPB_H
4 #define _CDS_URCU_DETAILS_GPB_H
7 #include <cds/urcu/details/gp.h>
8 #include <cds/algo/backoff_strategy.h>
9 #include <cds/container/vyukov_mpmc_cycle_queue.h>
11 namespace cds { namespace urcu {
13 /// User-space general-purpose RCU with deferred (buffered) reclamation
15 @headerfile cds/urcu/general_buffered.h
17 This URCU implementation contains an internal buffer where retired objects are
18 accumulated. When the buffer becomes full, the RCU \p synchronize function is called
19 that waits until all reader/updater threads end up their read-side critical sections,
20 i.e. until the RCU quiescent state will come. After that the buffer and all retired objects are freed.
21 This synchronization cycle may be called in any thread that calls \p retire_ptr function.
23 The \p Buffer contains items of \ref cds_urcu_retired_ptr "retired_ptr" type and it should support a queue interface with
25 - <tt> bool push( retired_ptr& p ) </tt> - places the retired pointer \p p into queue. If the function
26 returns \p false it means that the buffer is full and RCU synchronization cycle must be processed.
27 - <tt>bool pop( retired_ptr& p ) </tt> - pops queue's head item into \p p parameter; if the queue is empty
28 this function must return \p false
29 - <tt>size_t size()</tt> - returns queue's item count.
31 The buffer is considered as full if \p push returns \p false or the buffer size reaches the RCU threshold.
33 There is a wrapper \ref cds_urcu_general_buffered_gc "gc<general_buffered>" for \p %general_buffered class
34 that provides unified RCU interface. You should use this wrapper class instead \p %general_buffered
37 - \p Buffer - buffer type. Default is cds::container::VyukovMPMCCycleQueue
38 - \p Lock - mutex type, default is \p std::mutex
39 - \p Backoff - back-off schema, default is cds::backoff::Default
42 class Buffer = cds::container::VyukovMPMCCycleQueue<
44 ,cds::opt::buffer< cds::opt::v::dynamic_buffer< epoch_retired_ptr > >
46 ,class Lock = std::mutex
47 ,class Backoff = cds::backoff::Default
49 class general_buffered: public details::gp_singleton< general_buffered_tag >
52 typedef details::gp_singleton< general_buffered_tag > base_class;
55 typedef general_buffered_tag rcu_tag ; ///< RCU tag
56 typedef Buffer buffer_type ; ///< Buffer type
57 typedef Lock lock_type ; ///< Lock type
58 typedef Backoff back_off ; ///< Back-off type
60 typedef base_class::thread_gc thread_gc ; ///< Thread-side RCU part
61 typedef typename thread_gc::scoped_lock scoped_lock ; ///< Access lock class
63 static bool const c_bBuffered = true ; ///< This RCU buffers disposed elements
67 typedef details::gp_singleton_instance< rcu_tag > singleton_ptr;
73 CDS_ATOMIC::atomic<uint64_t> m_nCurEpoch;
75 size_t const m_nCapacity;
79 /// Returns singleton instance
80 static general_buffered * instance()
82 return static_cast<general_buffered *>( base_class::instance() );
84 /// Checks if the singleton is created and ready to use
87 return singleton_ptr::s_pRCU != nullptr;
92 general_buffered( size_t nBufferCapacity )
93 : m_Buffer( nBufferCapacity )
95 , m_nCapacity( nBufferCapacity )
100 clear_buffer( (uint64_t) -1 );
106 base_class::flip_and_wait( bkoff );
109 void clear_buffer( uint64_t nEpoch )
112 while ( m_Buffer.pop( p )) {
113 if ( p.m_nEpoch <= nEpoch )
122 // Return: true - synchronize has been called, false - otherwise
123 bool push_buffer( epoch_retired_ptr& ep )
125 bool bPushed = m_Buffer.push( ep );
126 if ( !bPushed || m_Buffer.size() >= capacity() ) {
137 /// Creates singleton object
139 The \p nBufferCapacity parameter defines RCU threshold.
141 static void Construct( size_t nBufferCapacity = 256 )
143 if ( !singleton_ptr::s_pRCU )
144 singleton_ptr::s_pRCU = new general_buffered( nBufferCapacity );
147 /// Destroys singleton object
148 static void Destruct( bool bDetachAll = false )
151 instance()->clear_buffer( (uint64_t) -1 );
153 instance()->m_ThreadList.detach_all();
155 singleton_ptr::s_pRCU = nullptr;
160 /// Retire \p p pointer
162 The method pushes \p p pointer to internal buffer.
163 When the buffer becomes full \ref synchronize function is called
164 to wait for the end of grace period and then to free all pointers from the buffer.
166 virtual void retire_ptr( retired_ptr& p )
169 epoch_retired_ptr ep( p, m_nCurEpoch.load( CDS_ATOMIC::memory_order_relaxed ));
174 /// Retires the pointer chain [\p itFirst, \p itLast)
175 template <typename ForwardIterator>
176 void batch_retire( ForwardIterator itFirst, ForwardIterator itLast )
178 uint64_t nEpoch = m_nCurEpoch.load( CDS_ATOMIC::memory_order_relaxed );
179 while ( itFirst != itLast ) {
180 epoch_retired_ptr ep( *itFirst, nEpoch );
186 /// Wait to finish a grace period and then clear the buffer
189 epoch_retired_ptr ep( retired_ptr(), m_nCurEpoch.load( CDS_ATOMIC::memory_order_relaxed ));
194 bool synchronize( epoch_retired_ptr& ep )
197 CDS_ATOMIC::atomic_thread_fence( CDS_ATOMIC::memory_order_acquire );
199 cds::lock::scoped_lock<lock_type> sl( m_Lock );
200 if ( ep.m_p && m_Buffer.push( ep ) )
202 nEpoch = m_nCurEpoch.fetch_add( 1, CDS_ATOMIC::memory_order_relaxed );
206 clear_buffer( nEpoch );
207 CDS_ATOMIC::atomic_thread_fence( CDS_ATOMIC::memory_order_release );
212 /// Returns internal buffer capacity
213 size_t capacity() const
219 }} // namespace cds::urcu
221 #endif // #ifndef _CDS_URCU_DETAILS_GPB_H