| /* |
| Copyright 2005-2010 Intel Corporation. All Rights Reserved. |
| |
| This file is part of Threading Building Blocks. |
| |
| Threading Building Blocks is free software; you can redistribute it |
| and/or modify it under the terms of the GNU General Public License |
| version 2 as published by the Free Software Foundation. |
| |
| Threading Building Blocks is distributed in the hope that it will be |
| useful, but WITHOUT ANY WARRANTY; without even the implied warranty |
| of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with Threading Building Blocks; if not, write to the Free Software |
| Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| |
| As a special exception, you may use this file as part of a free software |
| library without restriction. Specifically, if other files instantiate |
| templates or use macros or inline functions from this file, or you compile |
| this file and link it with other files to produce an executable, this |
| file does not by itself cause the resulting executable to be covered by |
| the GNU General Public License. This exception does not however |
| invalidate any other reasons why the executable file might be covered by |
| the GNU General Public License. |
| */ |
| |
| #ifndef __TBB_spin_rw_mutex_H |
| #define __TBB_spin_rw_mutex_H |
| |
| #include "tbb_stddef.h" |
| #include "tbb_machine.h" |
| #include "tbb_profiling.h" |
| |
| namespace tbb { |
| |
| class spin_rw_mutex_v3; |
| typedef spin_rw_mutex_v3 spin_rw_mutex; |
| |
| //! Fast, unfair, spinning reader-writer lock with backoff and writer-preference |
| /** @ingroup synchronization */ |
| class spin_rw_mutex_v3 { |
| //! @cond INTERNAL |
| |
| //! Internal acquire write lock. |
| bool __TBB_EXPORTED_METHOD internal_acquire_writer(); |
| |
| //! Out of line code for releasing a write lock. |
| /** This code is has debug checking and instrumentation for Intel(R) Thread Checker and Intel(R) Thread Profiler. */ |
| void __TBB_EXPORTED_METHOD internal_release_writer(); |
| |
| //! Internal acquire read lock. |
| void __TBB_EXPORTED_METHOD internal_acquire_reader(); |
| |
| //! Internal upgrade reader to become a writer. |
| bool __TBB_EXPORTED_METHOD internal_upgrade(); |
| |
| //! Out of line code for downgrading a writer to a reader. |
| /** This code is has debug checking and instrumentation for Intel(R) Thread Checker and Intel(R) Thread Profiler. */ |
| void __TBB_EXPORTED_METHOD internal_downgrade(); |
| |
| //! Internal release read lock. |
| void __TBB_EXPORTED_METHOD internal_release_reader(); |
| |
| //! Internal try_acquire write lock. |
| bool __TBB_EXPORTED_METHOD internal_try_acquire_writer(); |
| |
| //! Internal try_acquire read lock. |
| bool __TBB_EXPORTED_METHOD internal_try_acquire_reader(); |
| |
| //! @endcond |
| public: |
| //! Construct unacquired mutex. |
| spin_rw_mutex_v3() : state(0) { |
| #if TBB_USE_THREADING_TOOLS |
| internal_construct(); |
| #endif |
| } |
| |
| #if TBB_USE_ASSERT |
| //! Destructor asserts if the mutex is acquired, i.e. state is zero. |
| ~spin_rw_mutex_v3() { |
| __TBB_ASSERT( !state, "destruction of an acquired mutex"); |
| }; |
| #endif /* TBB_USE_ASSERT */ |
| |
| //! The scoped locking pattern |
| /** It helps to avoid the common problem of forgetting to release lock. |
| It also nicely provides the "node" for queuing locks. */ |
| class scoped_lock : internal::no_copy { |
| public: |
| //! Construct lock that has not acquired a mutex. |
| /** Equivalent to zero-initialization of *this. */ |
| scoped_lock() : mutex(NULL), is_writer(false) {} |
| |
| //! Acquire lock on given mutex. |
| scoped_lock( spin_rw_mutex& m, bool write = true ) : mutex(NULL) { |
| acquire(m, write); |
| } |
| |
| //! Release lock (if lock is held). |
| ~scoped_lock() { |
| if( mutex ) release(); |
| } |
| |
| //! Acquire lock on given mutex. |
| void acquire( spin_rw_mutex& m, bool write = true ) { |
| __TBB_ASSERT( !mutex, "holding mutex already" ); |
| is_writer = write; |
| mutex = &m; |
| if( write ) mutex->internal_acquire_writer(); |
| else mutex->internal_acquire_reader(); |
| } |
| |
| //! Upgrade reader to become a writer. |
| /** Returns true if the upgrade happened without re-acquiring the lock and false if opposite */ |
| bool upgrade_to_writer() { |
| __TBB_ASSERT( mutex, "lock is not acquired" ); |
| __TBB_ASSERT( !is_writer, "not a reader" ); |
| is_writer = true; |
| return mutex->internal_upgrade(); |
| } |
| |
| //! Release lock. |
| void release() { |
| __TBB_ASSERT( mutex, "lock is not acquired" ); |
| spin_rw_mutex *m = mutex; |
| mutex = NULL; |
| #if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT |
| if( is_writer ) m->internal_release_writer(); |
| else m->internal_release_reader(); |
| #else |
| if( is_writer ) __TBB_AtomicAND( &m->state, READERS ); |
| else __TBB_FetchAndAddWrelease( &m->state, -(intptr_t)ONE_READER); |
| #endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */ |
| } |
| |
| //! Downgrade writer to become a reader. |
| bool downgrade_to_reader() { |
| #if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT |
| __TBB_ASSERT( mutex, "lock is not acquired" ); |
| __TBB_ASSERT( is_writer, "not a writer" ); |
| mutex->internal_downgrade(); |
| #else |
| __TBB_FetchAndAddW( &mutex->state, ((intptr_t)ONE_READER-WRITER)); |
| #endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */ |
| is_writer = false; |
| |
| return true; |
| } |
| |
| //! Try acquire lock on given mutex. |
| bool try_acquire( spin_rw_mutex& m, bool write = true ) { |
| __TBB_ASSERT( !mutex, "holding mutex already" ); |
| bool result; |
| is_writer = write; |
| result = write? m.internal_try_acquire_writer() |
| : m.internal_try_acquire_reader(); |
| if( result ) |
| mutex = &m; |
| return result; |
| } |
| |
| private: |
| //! The pointer to the current mutex that is held, or NULL if no mutex is held. |
| spin_rw_mutex* mutex; |
| |
| //! If mutex!=NULL, then is_writer is true if holding a writer lock, false if holding a reader lock. |
| /** Not defined if not holding a lock. */ |
| bool is_writer; |
| }; |
| |
| // Mutex traits |
| static const bool is_rw_mutex = true; |
| static const bool is_recursive_mutex = false; |
| static const bool is_fair_mutex = false; |
| |
| // ISO C++0x compatibility methods |
| |
| //! Acquire writer lock |
| void lock() {internal_acquire_writer();} |
| |
| //! Try acquiring writer lock (non-blocking) |
| /** Return true if lock acquired; false otherwise. */ |
| bool try_lock() {return internal_try_acquire_writer();} |
| |
| //! Release lock |
| void unlock() { |
| #if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT |
| if( state&WRITER ) internal_release_writer(); |
| else internal_release_reader(); |
| #else |
| if( state&WRITER ) __TBB_AtomicAND( &state, READERS ); |
| else __TBB_FetchAndAddWrelease( &state, -(intptr_t)ONE_READER); |
| #endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */ |
| } |
| |
| // Methods for reader locks that resemble ISO C++0x compatibility methods. |
| |
| //! Acquire reader lock |
| void lock_read() {internal_acquire_reader();} |
| |
| //! Try acquiring reader lock (non-blocking) |
| /** Return true if reader lock acquired; false otherwise. */ |
| bool try_lock_read() {return internal_try_acquire_reader();} |
| |
| private: |
| typedef intptr_t state_t; |
| static const state_t WRITER = 1; |
| static const state_t WRITER_PENDING = 2; |
| static const state_t READERS = ~(WRITER | WRITER_PENDING); |
| static const state_t ONE_READER = 4; |
| static const state_t BUSY = WRITER | READERS; |
| //! State of lock |
| /** Bit 0 = writer is holding lock |
| Bit 1 = request by a writer to acquire lock (hint to readers to wait) |
| Bit 2..N = number of readers holding lock */ |
| state_t state; |
| |
| void __TBB_EXPORTED_METHOD internal_construct(); |
| }; |
| |
| __TBB_DEFINE_PROFILING_SET_NAME(spin_rw_mutex) |
| |
| } // namespace tbb |
| |
| #endif /* __TBB_spin_rw_mutex_H */ |