| /* |
| 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_queuing_rw_mutex_H |
| #define __TBB_queuing_rw_mutex_H |
| |
| #include "tbb_config.h" |
| |
| #if !TBB_USE_EXCEPTIONS && _MSC_VER |
| // Suppress "C++ exception handler used, but unwind semantics are not enabled" warning in STL headers |
| #pragma warning (push) |
| #pragma warning (disable: 4530) |
| #endif |
| |
| #include <cstring> |
| |
| #if !TBB_USE_EXCEPTIONS && _MSC_VER |
| #pragma warning (pop) |
| #endif |
| |
| #include "atomic.h" |
| #include "tbb_profiling.h" |
| |
| namespace tbb { |
| |
| //! Reader-writer lock with local-only spinning. |
| /** Adapted from Krieger, Stumm, et al. pseudocode at |
| http://www.eecg.toronto.edu/parallel/pubs_abs.html#Krieger_etal_ICPP93 |
| @ingroup synchronization */ |
| class queuing_rw_mutex { |
| public: |
| //! Construct unacquired mutex. |
| queuing_rw_mutex() { |
| q_tail = NULL; |
| #if TBB_USE_THREADING_TOOLS |
| internal_construct(); |
| #endif |
| } |
| |
| //! Destructor asserts if the mutex is acquired, i.e. q_tail is non-NULL |
| ~queuing_rw_mutex() { |
| #if TBB_USE_ASSERT |
| __TBB_ASSERT( !q_tail, "destruction of an acquired mutex"); |
| #endif |
| } |
| |
| class scoped_lock; |
| friend class scoped_lock; |
| |
| //! 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 { |
| //! Initialize fields |
| void initialize() { |
| mutex = NULL; |
| #if TBB_USE_ASSERT |
| state = 0xFF; // Set to invalid state |
| internal::poison_pointer(next); |
| internal::poison_pointer(prev); |
| #endif /* TBB_USE_ASSERT */ |
| } |
| public: |
| //! Construct lock that has not acquired a mutex. |
| /** Equivalent to zero-initialization of *this. */ |
| scoped_lock() {initialize();} |
| |
| //! Acquire lock on given mutex. |
| scoped_lock( queuing_rw_mutex& m, bool write=true ) { |
| initialize(); |
| acquire(m,write); |
| } |
| |
| //! Release lock (if lock is held). |
| ~scoped_lock() { |
| if( mutex ) release(); |
| } |
| |
| //! Acquire lock on given mutex. |
| void acquire( queuing_rw_mutex& m, bool write=true ); |
| |
| //! Try acquire lock on given mutex. |
| bool try_acquire( queuing_rw_mutex& m, bool write=true ); |
| |
| //! Release lock. |
| void release(); |
| |
| //! 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(); |
| |
| //! Downgrade writer to become a reader. |
| bool downgrade_to_reader(); |
| |
| private: |
| //! The pointer to the current mutex to work |
| queuing_rw_mutex* mutex; |
| |
| //! The pointer to the previous and next competitors for a mutex |
| scoped_lock * prev, * next; |
| |
| typedef unsigned char state_t; |
| |
| //! State of the request: reader, writer, active reader, other service states |
| atomic<state_t> state; |
| |
| //! The local spin-wait variable |
| /** Corresponds to "spin" in the pseudocode but inverted for the sake of zero-initialization */ |
| unsigned char going; |
| |
| //! A tiny internal lock |
| unsigned char internal_lock; |
| |
| //! Acquire the internal lock |
| void acquire_internal_lock(); |
| |
| //! Try to acquire the internal lock |
| /** Returns true if lock was successfully acquired. */ |
| bool try_acquire_internal_lock(); |
| |
| //! Release the internal lock |
| void release_internal_lock(); |
| |
| //! Wait for internal lock to be released |
| void wait_for_release_of_internal_lock(); |
| |
| //! A helper function |
| void unblock_or_wait_on_internal_lock( uintptr_t ); |
| }; |
| |
| void __TBB_EXPORTED_METHOD internal_construct(); |
| |
| // Mutex traits |
| static const bool is_rw_mutex = true; |
| static const bool is_recursive_mutex = false; |
| static const bool is_fair_mutex = true; |
| |
| private: |
| //! The last competitor requesting the lock |
| atomic<scoped_lock*> q_tail; |
| |
| }; |
| |
| __TBB_DEFINE_PROFILING_SET_NAME(queuing_rw_mutex) |
| |
| } // namespace tbb |
| |
| #endif /* __TBB_queuing_rw_mutex_H */ |