--- /dev/null
+/*
+ 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_SPINLOCK_H
+#define CDSLIB_SYNC_SPINLOCK_H
+
+#include <cds/algo/atomic.h>
+#include <cds/os/thread.h>
+#include <cds/algo/backoff_strategy.h>
+
+namespace cds {
+ /// Synchronization primitives
+ namespace sync {
+ /// Spin lock
+ /**
+ Simple and light-weight spin-lock critical section
+ It is useful to gain access to small (short-timed) code
+
+ Algorithm:
+
+ TATAS (test-and-test-and-lock)
+ [1984] L. Rudolph, Z. Segall. Dynamic Decentralized Cache Schemes for MIMD Parallel Processors.
+
+ No serialization performed - any of waiting threads may owns the spin-lock.
+ This spin-lock is NOT recursive: the thread owned the lock cannot call \p lock() method without deadlock.
+ The method \p unlock() can call any thread
+
+ DEBUG version: The spinlock stores owner thead id. Assertion is raised when:
+ - double lock attempt encountered by same thread (deadlock)
+ - unlock by another thread
+
+ If spin-lock is locked the \p Backoff algorithm is called. Predefined \p backoff::LockDefault class yields current
+ thread and repeats lock attempts later
+
+ Template parameters:
+ - \p Backoff - backoff strategy. Used when spin lock is locked
+ */
+ template <typename Backoff >
+ class spin_lock
+ {
+ public:
+ typedef Backoff backoff_strategy; ///< back-off strategy type
+ private:
+ atomics::atomic<bool> m_spin; ///< Spin
+# ifdef CDS_DEBUG
+ typename OS::ThreadId m_dbgOwnerId; ///< Owner thread id (only for debug mode)
+# endif
+
+ public:
+ /// Construct free (unlocked) spin-lock
+ spin_lock() noexcept
+# ifdef CDS_DEBUG
+ : m_dbgOwnerId( OS::c_NullThreadId )
+# endif
+ {
+ m_spin.store( false, atomics::memory_order_release );
+ }
+
+ /// Construct spin-lock in specified state
+ /**
+ In debug mode: if \p bLocked = true then spin-lock is made owned by current thread
+ */
+ explicit spin_lock( bool bLocked ) noexcept
+# ifdef CDS_DEBUG
+ : m_dbgOwnerId( bLocked ? cds::OS::get_current_thread_id() : cds::OS::c_NullThreadId )
+# endif
+ {
+ m_spin.store( bLocked, atomics::memory_order_release );
+ }
+
+ /// Dummy copy constructor
+ /**
+ The ctor initializes the spin to free (unlocked) state like the default ctor.
+ */
+ spin_lock(const spin_lock<Backoff>& ) noexcept
+ : m_spin( false )
+# ifdef CDS_DEBUG
+ , m_dbgOwnerId( cds::OS::c_NullThreadId )
+# endif
+ {
+ CDS_TSAN_ANNOTATE_MUTEX_CREATE( this );
+ }
+
+ /// Destructor. On debug time it checks whether spin-lock is free
+ ~spin_lock()
+ {
+ assert( !m_spin.load( atomics::memory_order_relaxed ));
+ CDS_TSAN_ANNOTATE_MUTEX_DESTROY( this );
+ }
+
+ /// Check if the spin is locked
+ bool is_locked() const noexcept
+ {
+ return m_spin.load( atomics::memory_order_relaxed );
+ }
+
+ /// Try to lock the object
+ /**
+ Returns \p true if locking is succeeded
+ otherwise (if the spin is already locked) returns \p false
+
+ Debug version: deadlock can be detected
+ */
+ bool try_lock() noexcept
+ {
+# ifdef CDS_THREAD_SANITIZER_ENABLED
+ bool bCurrent = m_spin.exchange( true, atomics::memory_order_acq_rel );
+ if ( !bCurrent )
+ CDS_TSAN_ANNOTATE_MUTEX_ACQUIRED( this );
+# else
+ bool bCurrent = m_spin.exchange( true, atomics::memory_order_acquire );
+# endif
+
+ CDS_DEBUG_ONLY(
+ if ( !bCurrent ) {
+ m_dbgOwnerId = OS::get_current_thread_id();
+ }
+ )
+ return !bCurrent;
+ }
+
+ /// Try to lock the object, repeat \p nTryCount times if failed
+ /**
+ Returns \p true if locking is succeeded
+ otherwise (if the spin is already locked) returns \p false
+ */
+ bool try_lock( unsigned int nTryCount ) noexcept( noexcept( backoff_strategy()()))
+ {
+ backoff_strategy backoff;
+ while ( nTryCount-- ) {
+ if ( try_lock())
+ return true;
+ backoff();
+ }
+ return false;
+ }
+
+ /// Lock the spin-lock. Waits infinitely while spin-lock is locked. Debug version: deadlock may be detected
+ void lock() noexcept(noexcept( backoff_strategy()()))
+ {
+ backoff_strategy backoff;
+
+ // Deadlock detected
+ CDS_TSAN_ANNOTATE_IGNORE_READS_BEGIN;
+ assert( m_dbgOwnerId != OS::get_current_thread_id());
+ CDS_TSAN_ANNOTATE_IGNORE_READS_END;
+
+ // TATAS algorithm
+ while ( !try_lock()) {
+ while ( m_spin.load( atomics::memory_order_acquire ))
+ backoff();
+ }
+
+ assert( m_dbgOwnerId == OS::get_current_thread_id());
+ }
+
+ /// Unlock the spin-lock. Debug version: deadlock may be detected
+ void unlock() noexcept
+ {
+ assert( m_spin.load( atomics::memory_order_relaxed ));
+ assert( m_dbgOwnerId == OS::get_current_thread_id());
+ CDS_DEBUG_ONLY( m_dbgOwnerId = OS::c_NullThreadId; )
+
+ CDS_TSAN_ANNOTATE_MUTEX_RELEASED( this );
+ m_spin.store( false, atomics::memory_order_release );
+ }
+ };
+
+ /// Spin-lock implementation default for the current platform
+ typedef spin_lock<backoff::LockDefault > spin;
+
+ /// Recursive spin lock.
+ /**
+ Allows recursive calls: the owner thread may recursive enter to critical section guarded by the spin-lock.
+
+ Template parameters:
+ - \p Integral one of integral atomic type: <tt>unsigned int</tt>, \p int, and others
+ - \p Backoff backoff strategy. Used when spin lock is locked
+ */
+ template <typename Integral, class Backoff>
+ class reentrant_spin_lock
+ {
+ typedef OS::ThreadId thread_id; ///< The type of thread id
+
+ public:
+ typedef Integral integral_type; ///< The integral type
+ typedef Backoff backoff_strategy; ///< The backoff type
+
+ private:
+ //@cond
+ atomics::atomic<integral_type> m_spin; ///< spin-lock atomic
+ thread_id m_OwnerId; ///< Owner thread id. If spin-lock is not locked it usually equals to \p OS::c_NullThreadId
+ //@endcond
+
+ private:
+ //@cond
+ void take( thread_id tid ) noexcept
+ {
+ m_OwnerId = tid;
+ }
+
+ void free() noexcept
+ {
+ m_OwnerId = OS::c_NullThreadId;
+ }
+
+ bool is_taken( thread_id tid ) const noexcept
+ {
+ return m_OwnerId == tid;
+ }
+
+ bool try_taken_lock( thread_id tid ) noexcept
+ {
+ if ( is_taken( tid )) {
+ m_spin.fetch_add( 1, atomics::memory_order_relaxed );
+ return true;
+ }
+ return false;
+ }
+
+ bool try_acquire() noexcept
+ {
+ integral_type nCurrent = 0;
+ bool bRet = m_spin.compare_exchange_weak( nCurrent, 1, atomics::memory_order_acquire, atomics::memory_order_acquire );
+
+# ifdef CDS_THREAD_SANITIZER_ENABLED
+ if ( bRet )
+ CDS_TSAN_ANNOTATE_MUTEX_ACQUIRED( this );
+# endif
+
+ return bRet;
+ }
+
+ bool try_acquire( unsigned int nTryCount ) noexcept( noexcept( backoff_strategy()()))
+ {
+ backoff_strategy bkoff;
+
+ while ( nTryCount-- ) {
+ if ( try_acquire())
+ return true;
+ bkoff();
+ }
+ return false;
+ }
+
+ void acquire() noexcept( noexcept( backoff_strategy()()))
+ {
+ // TATAS algorithm
+ backoff_strategy bkoff;
+ while ( !try_acquire()) {
+ while ( m_spin.load( atomics::memory_order_acquire ))
+ bkoff();
+ }
+ }
+ //@endcond
+
+ public:
+ /// Default constructor initializes spin to free (unlocked) state
+ reentrant_spin_lock() noexcept
+ : m_spin(0)
+ , m_OwnerId( OS::c_NullThreadId )
+ {
+ CDS_TSAN_ANNOTATE_MUTEX_CREATE( this );
+ }
+
+ /// Dummy copy constructor
+ /**
+ In theory, spin-lock cannot be copied. However, it is not practical.
+ Therefore, we provide dummy copy constructor that do no copy in fact. The ctor
+ initializes the spin to free (unlocked) state like default ctor.
+ */
+ reentrant_spin_lock( const reentrant_spin_lock<Integral, Backoff>& ) noexcept
+ : m_spin(0)
+ , m_OwnerId( OS::c_NullThreadId )
+ {
+ CDS_TSAN_ANNOTATE_MUTEX_CREATE( this );
+ }
+
+ /// Construct object in specified state
+ explicit reentrant_spin_lock( bool bLocked )
+ : m_spin(0)
+ , m_OwnerId( OS::c_NullThreadId )
+ {
+ CDS_TSAN_ANNOTATE_MUTEX_CREATE( this );
+ if ( bLocked )
+ lock();
+ }
+
+ /// Dtor. Spin-lock must be unlocked
+ ~reentrant_spin_lock()
+ {
+ assert( m_spin.load( atomics::memory_order_acquire ) == 0 );
+ assert( m_OwnerId == OS::c_NullThreadId );
+
+ CDS_TSAN_ANNOTATE_MUTEX_DESTROY( this );
+ }
+
+ /// Checks if the spin is locked
+ /**
+ The spin is locked if lock count > 0 and the current thread is not an owner of the lock.
+ Otherwise (i.e. lock count == 0 or the curren thread owns the spin) the spin is unlocked.
+ */
+ bool is_locked() const noexcept
+ {
+ return !( m_spin.load( atomics::memory_order_relaxed ) == 0 || is_taken( cds::OS::get_current_thread_id()));
+ }
+
+ /// Try to lock the spin-lock
+ bool try_lock() noexcept( noexcept( std::declval<reentrant_spin_lock>().try_acquire()))
+ {
+ thread_id tid = OS::get_current_thread_id();
+ if ( try_taken_lock( tid ))
+ return true;
+ if ( try_acquire()) {
+ take( tid );
+ return true;
+ }
+ return false;
+ }
+
+ /// Try to lock up to \p nTryCount attempts
+ bool try_lock( unsigned int nTryCount ) noexcept( noexcept( std::declval<reentrant_spin_lock>().try_acquire( nTryCount )))
+ {
+ thread_id tid = OS::get_current_thread_id();
+ if ( try_taken_lock( tid ))
+ return true;
+ if ( try_acquire( nTryCount )) {
+ take( tid );
+ return true;
+ }
+ return false;
+ }
+
+ /// Lock the object waits if it is busy
+ void lock() noexcept( noexcept( std::declval<reentrant_spin_lock>().acquire()))
+ {
+ thread_id tid = OS::get_current_thread_id();
+ if ( !try_taken_lock( tid )) {
+ acquire();
+ take( tid );
+ }
+ }
+
+ /// Unlock the spin-lock
+ void unlock() noexcept
+ {
+ assert( is_taken( OS::get_current_thread_id()));
+
+ integral_type n = m_spin.load( atomics::memory_order_relaxed );
+ if ( n > 1 )
+ m_spin.store( n - 1, atomics::memory_order_relaxed );
+ else {
+ free();
+ CDS_TSAN_ANNOTATE_MUTEX_RELEASED( this );
+ m_spin.store( 0, atomics::memory_order_release );
+ }
+ }
+
+ /// Change the owner of locked spin-lock. May be called by thread that owns spin-lock
+ void change_owner( OS::ThreadId newOwnerId ) noexcept
+ {
+ assert( is_taken( OS::get_current_thread_id()));
+ assert( newOwnerId != OS::c_NullThreadId );
+
+ m_OwnerId = newOwnerId;
+ }
+ };
+
+ /// Recursive 32bit spin-lock
+ typedef reentrant_spin_lock<uint32_t, backoff::LockDefault> reentrant_spin32;
+
+ /// Default recursive spin-lock
+ typedef reentrant_spin32 reentrant_spin;
+
+ /// Recursive 64bit spin-lock
+ typedef reentrant_spin_lock<uint64_t, backoff::LockDefault> reentrant_spin64;
+ } // namespace sync
+} // namespace cds
+
+#endif // #ifndef CDSLIB_SYNC_SPINLOCK_H
projects / c11concurrency-benchmarks.git / blobdiff